THE  LIBRARY 

OF 
THE  UNIVERSITY 

OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


PROCEEDINGS 

OF  THE 

,  WASHINGTON   ACADEMY  OF   SCIENCES 

VOL.  IX,  PP.  79-158  PLATES  \-XV  JULY  31,  1907 


DISTRIBUTION  OF  THE  SUBCUTANEOUS  VESSELS 

IN  THE  HEAD  REGION  OF  THE  GANOIDS, 

POLYODON  AND  LEPISOSTEUS. 


WM.    F.    ALLEN. 
(FROM  THE  STANFORD  MARINE  LABORATORY,  PACIFIC  GROVE,  CALIF.) 


WASHINGTON,  D.  C. 
PUBLISHED  BY  THE  ACADEMY 

1907 


, 


PROCKKDINOS 

OF  THE 

;  WASHINGTON  ACADEMY  OF  SCIENCES 

VOL.  IXr  PP.  79-158.  PLATES  I-XV.  JULY  31,  1907. 


DISTRIBUTION  OF  THE  SUBCUTANEOUS  VESSELS 

IN  THE  HEAD  REGION  OF  THE  GANOIDS, 

POLYODON  AND  LEPISOSTEUS. 

BY  WM.  F.  ALLEN. 
(FROM  THE  STANFORD  MARINE  LABORATORY,  PACIFIC  GROVE,  CALIF.) 

CONTENTS. 

PAGE. 

I.   Introduction 80 

Material 80 

Method  of  Procedure 80 

History 82 

II.    Distribution  of  the  Subcutaneous  Vessels  in  Poly odon 94 

1.  Cephalic  Sinuses  and  their  Connections 94 

Cephalic  Lymphatic  Trunk 96 

Hyo-opercularis  Sinus 98 

Hyo-opercularis  Lymphatic  Trunk 98 

Facial  Lymphatic  Trunks 100 

2.  Branchial  Lymphatics  (Nutrient  Branchial  Veins?) 101 

Branchial  Arch  Lymphatics  (Nutrient  Veins?) 103 

Respiratory  and  Nutrient  Branchial  Arteries 106 

Dorsal  and  Ventral  Endings  of  the  Branchial  Lymphatic  Trunks 

(Nutrient  Branchial  Veins?) 108 

Lymphoid  Tissue  Surrounding  the  Heart  of  Polyodon 108 

III.  Distribution  of  the  Subcutaneous  Vessels  in  Lepisosteus 113 

Longitudinal  Lymphatic  Trunks 113 

Pericardial  Sinuses 114 

Occipital  Sinus 115 

Branchial  Lymphatic  Sinuses 117 

Hyo-opercularis  Sinus 118 

Cephalic  Sinus 118 

Branchial  Lymphatic  Trunks  (Nutrient  Veins?) 119 

Inferior  Jugular  Vein , 121 

IV.  Deductions  and  Summary 121 

V.  Explanation  of  Plates 126 

VI.  List  of  Abbreviations  Used  in  the  Figures 155 

Proc.  Wash.  Acad.  Sci.,  July,  1907.  79 


8O  ALLEN 

I.    INTRODUCTION. 

Material.  —  The  Ganoids  used  for  this  problem  consisted  of 
Polyodon  spathula  (spoon-bill  cat),  Lepisosteus  tristcechus  (alli- 
gator gar),  Lepisosteus  osseus  (spike-bill  gar),  and  Lepisosteus 
platostomus  (duck-bill  gar),  which  are  the  most  common  Ganoids 
found  on  the  mud  bars  and  in  the  sloughs  of  the  Ohio  and  Mis- 
sissippi rivers  about  Cairo,  Illinois.  The  fish  were  mostly  taken 
through  seining  by  moonlight ;  for  it  is  at  night  that  they  leave 
the  channels  to  do  their  feeding  on  the  bars.  L.  tristcechus  is 
by  far  the  largest  of  the  Lepisosteidce  and  I  at  first  hoped  to  use 
it  as  a  type  for  the  RHOMBOGANOIDEA,  but  found  it  necessary 
to  give  it  up  for  the  following  reasons:  L.  tristcechus  could 
only  be  obtained  during  the  fall  of  the  year.  Other  things  being 
equal  it  was  always  able  to  force  its  way  through  the  seine,  and 
the  large  specimens  were  found  too  massive  to  inject  and  pickle 
conveniently.  Consequently  most  of  the  injections  and  dissec- 
tions were  made  on  L.  osseus,  which  differed  from  L.  platos- 
tomus in  no  important  detail,  but  which  was  found  to  be  more 
suitable  for  these  investigations. 

Most  of  the  dissections  were  made  during  what  spare  time  I 
had,  while  engaged  in  somewhat  similar  work  for  Mr.  E.  P. 
Allis,  Jr.,  at  Cairo,  Illinois,  and  the  work  was  continued  when 
called  by  him  to  the  Stanford  Marine  Laboratory  at  Pacific 
Grove,  California. 

Method  of  Procedure.  —  As  in  my  previous  studies  Hoyer's 
lead  chromate  gelatin  mass  and  a  Berlin  blue  gelatin  mass 
were  the  injecting  media  used.  Ordinarily  the  blood  vessels 
were  first  injected  with  the  blue  mass,  and  the  subcutaneous 
vessels  were  afterward  filled  with  the  yellow.  Instead  of  making 
my  own  soluable  blue  as  formerly,  I  found  that  wJhat  is  sold  by 
druggists  as  Tiernan's  soluble  Prussian  blue  was  equally  satis- 
factory and  involved  far  less  labor.  Since  all  that  is  necessary 
is  to  add  200  c.c.  of  concentrated  Prussian  blue  solution,  pref- 
erably hot,  to  a  hot  solution  of  25  gr.  of  gelatin  that  had  been 
expanded  in  100  c.c.  of  water. 

In  nearly  every  case  the  head  was  severed  from  the  body  a 
short  distance  behind  the  shoulder  girdle,  the  intestine  cut  at 
the  rectum,  and  the  viscera  pulled  out  with  the  head.  With 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     8l 

Polyodon  this  was  a  very  simple  matter;  while  with  the  Lepi- 
sosteidae  which  have  such  a  bulwark  of  armor  it  was  necessary 
first  v£aj-ejujjy^to)remove  entirely  two  or  three  rows  of  scales  a 
little  back  from  the  shoulder  girdle.  Great  care  should  be 
exercised  in  this  operation  for  the  delicate  longitudinal  lym- 
phatic trunks  are  very  firmly  attached  to  the  scales  by  connec- 
tive tissue.  When  this  is  completed  the  body  can  be  severed 
as  easily  as  Polyodon.  Usually  the  blood  vessels  of  Polyodon 
were  first  injected  from  the  cut  aorta,  but  with  the  Lepisosteidae 
this  was  not  deemed  necessary.  With  the  Lepisosteidae  the  cut 
ends  of  the  dorsal,  ventral,  and  one  of  the  lateral  lymphatic 
trunks  were  first  plugged  with  cotton,  and  the  injection  was 
made  from  the  remaining  lateral  trunk.  Since  no  dorsal  and 
ventral  lymphatic  trunks  were  found  in  this  region  in  Polyodon 
it  was  only  necessary  to  stop  up  one  of  the  lateral  trunks  and 
inject  from  the  other.  After  the  cephalic  sinus  and  its  poste- 
rior connections  had  been  worked  out  in  Polyodon  it  was  found 
that  a  more  satisfactory  injection  of  the  cephalic  trunks  could 
be  obtained  by  injecting  the  so-called  cephalic  lymphatic  trunk, 
forward,  from  a  point  designated  by  (#)  in  Fig.  i.  During  the 
summer  months  the  heat  was  so  intense  at  Cairo  that  the  gelatin 
injecting  mass  in  the  vessels  would  not  solidify  unless  the  head 
was  first  placed  in  a  bath  of  ice  water.  When  once  the  mass 
was  hard  and  the  specimen  placed  in  formalin  it  was  found  that 
no  amount  of  summer  temperature  would  liquefy  it. 

All  the  injected  microscopic  preparations  were  hardened  in 
formalin,  run  up  the  alcohols,  and  mounted  in  xylol-balsam. 
The  material  for  sectioning  was  fixed  in  Tellyesniczky's  potas- 
sium bichromate-acetic  mixture,  imbedded  in  paraffin,  cut  6  to 
ip  p.  thick,  stained  in  either  Heidenhain's  iron  haematoxylin  or 
Hansen's  haematoxylin  plus  2  per  cent,  glacial  acetic  acid,1  and 
counterstained  in  a  concentrated  alcoholic  solution  of  orange  G 
plus  a  small  per  cent,  of  acid  fuchsin. 

1  The  object  of  adding  the  2  per  cent,  glacial  acetic  to  Hansen's  solution  was 
to  do  away  with  the  precipitate  which  is  always  formed.  The  sections  thus 
stained  are  red,  but  rapidly  turn  to  a  brilliant  blue  when  placed  in  tap  water  that 
is  alkaline.  Formerly  hsemalum  was  used  for  a  simple  hsematoxylin  stain,  but 
my  experience  has  been  that  the  product  as  sold  commercially  varied  so  much 
that  it  could  not  be  relied  upon,  and  that  Hansen's  solution  was  superior  to  the 
strongest  haemalum. 


82  ALLEN 

History.  —  Since  looking  up  the  literature  for  my  recent 
paper  on  the  lymphatics  of  Scorp&nichthys1  several  very  in- 
teresting papers  by  Neuville,2  Vialleton,3  and  Jos-sifoo4  have 
been  received. 

Ever  since  the  subcutaneous  vessels  have  been  studied  there 
has  been  a  merry  war  on  as  to  whether  they  were  lymphatics  or 
veins,  but  so  far  as  I  am  aware  this  controversy  has  been  con- 
fined to  the  Selachians.  No  one  to  my  knowledge  has  described 
these  vessels  in  the  Teleostomi  as  veins.  In  the  Cyclostomi 
Miiller  (15, 5  p.  18)  describes  an  abdominal  lymphatic  trunk  in 
Myxine  as  running  along  beneath  the  chorda  dorsalis,  above  the 
aorta.  Throughout  the  body  cavity  it  receives  the  intercostals 
and  the  visceral  vessels.  Anterior  to  the  body  cavity  the  trunk 
divides,  each  fork  following  the  corresponding  row  of  gills. 
No  connection,  however,  with  the  venous  system  was  estab- 
lished. Jackson,  in  his  work  on  the  circulation  of  Bdellos- 
toma*  (p.  35),  observed  a  marked  tendency  for  the  injecting 
mass  to  escape  from  the  blood  vessels  to  the  subdermal  lym- 
phatic spaces  of  the  caudal  region  and  the  peri-branchial  spaces 
about  the  gill  pouches!  Vialleton7  (pp.  308-318),  under  the 
head  of  espaces  sereux  inter  stitiels,  gives  an  extended  and  most 
interesting  account  of  these  peri-branchial  spaces  in  Petromyzon 
•planeri  and  Ammocaetes.  It  seems  that  the  older  writers,  as 
Robin,  Milne-Edwards,  Nestler,  Vogt  and  Yung,  and  Schneider, 
regarded  these  spaces  as  blood  cavities  on  account  of  their  con- 
nection with  the  interior  jugular,  and  the  fact  that  Schneider 

1  "  Distribution  of  the  Lymphatics  in  the  Head,  and  in  the  Dorsal,  Pectoral, 
and  Ventral  Fins  of  Scorpcenichthys  ntarmoratus"  Proceedings  of  the  Wash- 
ington Academy  of  Sciences,  VIII,  1906,  pp.  41-90. 

2H.  Neuville,  "  Contribution  a  1'etude  de  la  vascularisation  intestinale  chez 
les  Cyclostomes  et  les  Selachiens."  Annales  des  Sciences  naturelles.  1901. 

3L.  Vialleton,  "  Les  lymphatiques  du  tube  digestif  de  la  Torpille  (Torpedo 
marmorata)."  Archives  d'  anatomie  microscopique.  1902. 

4S.  M.  Jossifoo,  "Sur  les  voies  principales  et  les  organes  de  propulsion  de  la 
lymphe  chez  certains  Poissons."  Arch.  d'Anat.  Micr.  1906. 

5  All  bibliographical  numbers  in  parentheses  refer  to  a  list  of  literature  in  a 
previous  paper.  See  footnote  Jk 

6C.  M.  Jackson,  "An  Investigation  of  the  Vascular  System  of  Bdellostoma 
dombeyi."  Bulletin  of  University  of  Cincinnati.  No.  5.  1901. 

7L.  Vialleton,  "Etude  sur  le  coeur  des  lamproies. "  Archives  d'^anatomie 
microscopique.  1903. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     83 

found  blood  in  these  spaces  is  accounted  for  by  Vialleton  as 
being  an  entirely  abnormal  condition,  which  is  brought  about 
by  a  hemorrhage  of  the  delicate  branchial  vessels  into  these 
cavities,  as  a  result  of  excitement  from  capture.  As  to  consid- 
ering these  spaces  lymphatic  cavities,  Vialleton  points  out  that 
they  differ  widely  from  other  cavities  designated  by  that  name, 
and  throws  out  a  strong  warning  about  the  abuse  of  that  term. 
Since  the  peri-branchial  spaces  are  only  developed  in  Petro- 
myzon  after  metamorphosis,  Vialleton  pronounces  these  cavities 
to  be  a  special  apparatus  adapted  to  the  movements  of  the  re- 
spiratory sacs.  Neuville  (of.  £/'/.,  p.  54),  in  opposition  to  the 
general  opinion,  holds  that  no  separate  chylous  system  is  to  be 
found  in  the  digestive  tract  of  the  Cyclostomes.  As  a  study  in 
comparative  anatomy  I  injected  the  blood  vessels  of  the  Pacific 
Bdellostoma  (=  Polistotremd)  and  found  that  the  intercostal 
arteries  alternated  with  the  intercostal  veins  in  supplying  the 
septa  between  two  myotomes,  there  being  but  one  blood-vessel 
for  each  septum,  but  for  each  septum  there  is  an  additional  inter- 
costal vessel  that  terminates  in  an  abdominal  sinus,  which  runs 
parallel  with  the  aorta.  This  system  we  take  to  be  lymphatic 
rather  than  a  separate  venous  system.  No  attempt  was  made 
to  determine  how  the  injecting  mass  reached  this  system ; 
whether  it  passed  through  venous-lymphatic  openings  or 
whether  it  broke  through  the  delicate  walls  of  the  blood- 
vessels. 

Robin  (23,  pp.  22-30)  gives  an  excellent  account  of  the  early 
work  of  Monro  and  Fohmann  on  the  lymphatics  of  the  Sela- 
chians. The  former,  it  seems  (14),  described  the  chylous  ves- 
sels of  the  viscera  fairly  well,  except  that  he  portrayed  the 
common  visceral  reservoir  as  continuing  along  the  vena  cava 
(cardinal)  in  order  to  empty  into  the  sinus  of  Monro  (precava  or 
ductus  Cuvieri) ;  while  according  to  Robin  (p.  2)  there  are  two 
triangular  reservoirs,  corresponding  in  position  to  the  two  car- 
dinal sinuses,  into  which  they  are  discharged.  Lymphatics  are 
indicated  as  coming  from  the  pectoral  fin,  brain,  eye,  and  ear, 
and  the  veine  jugulaire  anterieure  (inferior  jugular)  is  regarded 
as  a  lymphatic  trunk.  Monro  confused  the  lateral  line  canal 
for  a  lymphatic  trunk,  and  because  he  saw  the  injecting  mass 


84  ALLEN 

pass  out  of  the  pores,  concluded  that  this  system  also  arose  from 
free  openings  in  the  digestive  tract.  Robin  states  that  Foh- 
mann's  work  on  Torpedo  marmorata  (4)  contains  nothing  not 
found  in  Monro,  and  that  his  failure  to  inject  the  blood  vessels 
has  resulted  in  many  incorrect  relationships.  Fohmann  desig- 
nates the  common  chylous  reservoir  as  the  reservoir  de  Pccquet, 
and  finds  in  the  digestive  tract  many  connections  between  the 
small  veins  and  the  lymphatics.  He  has  not  found  muscle 
fibers  in  these  vessels,  but  considers  them  as  contractile,  and, 
contrary  to  Monro,  claims  that  they  do  not  possess  valves  save  at 
the  entrance  into  the  veins. 

Leydig  (12)  made  a  histological  study  of  the  lymphatics  of 
the  digestive  tract  of  Raja  batt's,  and  reached  the  conclusion 
that  the  blood  vessels  are  surrounded  by  chylous  vessels.  He 
was  the  first  to  describe  the  tubular  bodies,  turbanliche  Korper, 
that  encircle  the  lymphatic  vessels,  which  Sappey  and  Mayer 
have  so  fully  discussed. 

Robin  (23)  after  working  up  this  system  of  vessels  in  Torpedo 
galvanii  and  other  plagiostomes,  firmly  declares  (pp.  2  and  32) 
that  these  subcutaneous  vessels  are  veins,  and  that  the  chylous 
vessels  are  the  only  lymphatics  possessed  by  a  fish.  He  also 
describes  (pp.  15-16)  lymphatic  networks  arising  from  the  heart 
and  neighboring  trunks,  which  reach  the  veins  through  the 
intermedian  plexus  on  the  oesophagus  and  liver. 

Parker  (20,  pp.  720-1)  describes  these  subcutaneous  vessels 
in  Mustelus  antarcticus  under  the  head  of  cutaneous  veins,  and 
states  that  so  far  as  his  experience  goes  that  they  invariably 
contain  blood.  A  dorsal  cutaneous  vein  is  set  forth  as  extend- 
ing from  the  tail  to  some  distance  in  front  of  the  first  dorsal 
fin.  Behind  the  second  dorsal  it  forks ;  the  two  branches 
encircling  the  fin  unite  in  front  in  a  single  trunk,  which  when 
the  first  dorsal  is  reached  subdivides  into  three  branches,  two 
of  which  encircle  the  fin  to  reunite  in  front  while  the  median 
one  passes  ventrad  to  terminate  in  the  left  renal  portal.  An 
anterior  ventral  cutaneous  vein  extends  from  the  pubis  to 
the  shoulder  girdle.  It  is  located  between  the  skin  and  the 
abdominal  muscles,  and  receives  a  beautiful  plexus  from  the 
abdominal  wall.  "Anteriorly  the  vein  trifurcates,  the  three 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     85 

branches  uniting  again  in  the  form  of  a  rhomboid,  the  lateral 
angles  of  which  are  connected  with  the  lateral  veins."  Pos- 
teriorly it  bifurcates  and  both  branches  after  following  along 
the  border  of  the  pubic  cartilage  pass  inward  to  unite  with  the 
iliac  veins.  The  so-called  -posterior  ventral  cutaneous  vein 
starts  from  the  tail,  and  forming  a  loop  around  the  anals,  again 
unite  in  front  of  the  fin  to  bifurcate  in  the  cloaca  region  and 
empty  into  the  cloaca  veins.  Parker  notes  a  direct  communi- 
cation of  the  cloaca  veins  with  the  iliac,  so  that  the  anterior  and 
posterior  veins  might  be  represented  as  a  single  trunk  forming  a 
loop  around  the  anal  fin  and  the  cloaca.  Finally  the  two 
lateral  cutaneous  veins  are  described  and  figured  as  running 
along  the  side  of  the  trunk  at  the  junction  of  the  dorsal  and 
ventral  muscles.  Posteriorly  they  unite  with  the  caudal  and 
dorsal  cutaneous  veins,  and  anteriorly  they  terminate  in  sub- 
scapular  sinuses,  which  are  discharged  into  corresponding 
cardinal  sinuses. 

Sappey  (25)  undoubtedly  has  done  the  most  work  of  anyone 
on  these  subcutaneous  vessels,  and  unquestionably  pronounces 
them  as  lymphatics  in  the  ray,  dogfish  (Squalus),  and  in  several 
Teleosts.  In  these  different  groups  he  also  takes  up  in  detail 
the  distribution  of  the  blood  vessels  and  the  lateral  line  system. 
His  monograph  is  illustrated  by  12  large  lithographic  plates. 
In  a  ray  he  finds  these  subcutaneous  vessels  arising  from  the 
dorsal  and  ventral  surfaces  of  the  body,  from  the  mucous 
canals,  muscles,  electrical  apparatus,  viscera  and  heart.  Most 
of  the  lymphatics  on  the  dorsal  surface  of  the  body  are  described 
and  figured  (PI.  5,  Fig.  i)  as  being  in  communication  with  the 
grand  sinus  curviligne  (Fig.  i,  5)  which  lies  above  the  gills, 
and  near  its  posterior  extremity  communicates  with  the  ductus 
of  Cuvier  from  above.  Three  trunks  have  their  origin  from 
the  anterior  part  of  the  pectoral  fin  and  empty  into  this  reservoir, 
which  are  designated  from  cephalad  to  caudad  as  le  tronc  longi- 
tudinal (Fig.  i,  2),  le  tronc  lateral  anterieur,  and  le  tronc  lateral 
moyen.  Coming  in  from  the  rear  or  virtually  continuous  with 
the  sinus  curviligne  is  le  grand  sinus  longitudinal  (Fig.  i,  18). 
It  extends  caudad  to  the  tail,  and  at  the  point  of  opening  into 
the  sinus  curviligne  it  receives  le  tronc  lateral  -posterieur  (Fig. 


86  ALLEN 

i,  13),  which  drains  the  posterior  part  of  the  pectoral  fin.  At 
various  intervals  communicating  branches  are  received  from  le 
petit  sinus  longitudinal  (Fig.  i,  24),  which  runs  parallel  but 
median  to  the  grand  sinus.  In  the  lumbar  region  there  is  a 
rich  network  (Fig.  i,  16),  which  in  part  empties  into  le  grand 
sinus  longitudinal  and  in  part  into  its  anterior  branch  le  tronc 
lateral  posterieur.  Midway  between  the  pectoral  and  ventral 
fins  a  large  lateral  branch  is  given  off  (Fig.  i,  23)  to  communi- 
cate with  the  veins  at  the  articulation  of  the  ventral  fin,  Ics 
veines  extrapelviennes.  This  communicating  trunk  also  re- 
ceives the  rich  network  from  the  ventral  fin.  Two  lymphatic 
vessels  are  said  to  have  their  source  from  the  snout  region  and 
flow  toward  the  eye  (Fig.  i,  i).  The  outer  one  passes  behind 
the  eye  and  empties  into  the  internal  jugular  or  a  branch ; 
while  the  inner  one  terminates  in  like  manner  mesad  of  the 
eye. 

In  brief,  the  subcutaneous  vessels  from  the  ventral  surface  of 
the  body  are  set  forth  as  follows :  In  the  anterior  part  of  the 
pectoral,  laterad  of  the  mouth,  four  vessels  unite  in  a  common 
trunk  (PI.  VI,  Fig.  i,  6),  which  passes  dorsal  to  discharge  itself 
into  the  anterior  end  of  the  sinus  curviligne.  Two  of  these 
vessels  arise  from  the  anterior  part  of  the  pectoral  and  are 
designated  as  le  tronc  anterieur  (Fig.  i,  2)  and  le  tronc  moyen 
(Fig.  1,9);  while  the  other  two  come  from  the  median  portion 
of  the  body  and  are  named  le  tronc  cephalique  (Fig.  i,  i)  and 
le  tronc  thoracique  (Fig.  i,  8).  The  former  takes  its  origin 
from  the  snout  region  and  the  latter  from  the  region  immedi- 
ately behind  the  mouth.  Le  tronc  posterieur  (Fig.  i,  15)  col- 
lects the  lymph  from  the  posterior  part  of  the  pectoral  and  from 
the  abdomen ;  it  pierces  the  muscular  wall  to  unite  with  the 
common  vein  of  the  pectoral  fin.  Sappey  states  that  the  ab- 
dominal plexus  is  remarkable  for  the  fact  that  it  not  only  anas- 
tomoses with  the  networks  of  the  ventral  and  anal  fins,  but  in 
addition  there  are  numerous  communications  with  the  blood 
capillaries.  The  rich  network  of  the  anal  unites  in  a  great 
number  of  vessels  that  connect  with  those  of  the  cloaca  and  in- 
testine, and  without  a  definite  course  disappear  in  the  veins  of 
the  caudal  fin. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     87 

According  to  Sappey  the  chylous  vessels  terminate  in  the 
ductus  Curveri  through  a  right  and  left  trunk  (PI.  VII,  Fig.  5, 
7),  the  openings  being  guarded  by  valves. 

Sappey  (p.  32)  describes  a  lace-like  lymphatic  network  aris- 
ing from  the  heart,  especially  from  the  ventricle  and  bulbus, 
which  is  collected  by  two  trunks  (PI.  II,  Fig.  3,  3)  that  termi- 
nate in  the  sinus  of  Curver.  It  should  be  noted  that  these  two 
vessels  correspond  identically  with  what  Parker  (20,  p.  720) 
describes  and  figures  (PL  34,  Fig.  4,  Cor.  V.)  as  the  coronary 
veins. 

In  the  rays  Sappey  finds  numerous  muscular  bands  encircling 
the  lymphatics,  not  only  of  the  viscera  as  described  by  Leydig, 
but  also  in  all  parts  of  the  body.  Aside  from  the  digestive 
tract  he  figures  them  from  the  subcutaneous  and  intermuscular 
vessels  of  pectoral,  from  the  abdominal  and  thoracic  networks, 
and  from  the  networks  of  the  ventral  fin  and  lumbar  regions. 
When  he  first  discovered  them  in  1870  he  supposed  that  they 
were  characteristic  of  the  lymphatics  of  all  fish,  but  later  found 
them  only  in  the  rays.  Sappey  attributes  a  double  role  to  these 
so-called  lymphatic  hearts,  by  contracting  they  would  cause  a 
peristaltic  movement  in  these  vessels,  and  to  a  certain  extent 
would  also  take  the  place  of  valves. 

After  considering  the  lateral  line  system  and  the  blood  vessels 
of  Squalus  Sappey  takes  up  (pp.  37-40  and  PI.  X)  the  distri- 
bution of  the  lymphatic  system.  On  each  side  of  the  body  he 
finds  two  lateral  lymphatic  trunks,  superior  and  inferior  in  posi- 
tion. The  former  (Fig.  3,  2)  extends  from  the  tail  to  the  head, 
a  little  below  the  lateral  line.  In  the  tail  region  it  forms  a  sort 
of  fibrous  sinus  that  empties  into  the  caudal  vein ;  while  an- 
teriorly it  ends  with  the  inferior  trunk  in  a  sinus  or  confluent 
(Fig.  i,  25),  which  opens  into  the  precava,  near  its  origin.  The 
inferior  lateral  trunk  (Fig.  3,  n)  is  a  subcutaneous  vessel, 
traversing  in  a  median  line  from  the  tail  to  the  head,  where  it 
blends  with  the  superior  trunk  in  forming  a  single  vessel,  which 
terminates  in  the  cephalic  sinus  mentioned  above.  It  should 
not  be  confounded  with  the  corresponding  vein,  which  is  more 
profundus,  being  distinctly  submuscular.  Sappey  states  that 
the  inferior  trunk  is  sometimes  absent.  A  median  dorsal  trunk 


88  ALLEN 

(Fig.  i,  15,  and  Fig.  3,  4),  has  its  origin  in  the  tail  region.  In 
passing  cephalad  it  trifurcates  when  the  dorsal  fins  are  reached, 
the  two  outer  branches  receive  the  superficial  networks  and  the 
median  one  the  dorsal  and  ventral  branches  (Fig.  3,  8  and  9). 
In  front  of  the  fin  these  branches  unite  in  a  common  trunk, 
which  upon  reaching  the  cranium  bifurcates,  each  fork  making 
a  curve  behind  the  eye  to  empty  into  the  internal  jugular.  A 
median  abdominal  trunk  extends  from  the  ventral  fin  to  the 
clavicle,  where  it  bends  to  discharge  itself  into  the  sinus  of 
Cuvier.  Sometimes,  according  to  Sappey,  it  bifurcates,  and 
each  fork  terminates  in  the  corresponding  ductus  of  Cuvier. 
These  six  trunks  are  connected  by  a  series  of  vessels  into  which 
a  network  of  capillaries  are  discharged.  A  series  of  intercostals 
(Fig.  3,  13  and  14),  connect  the  ventral  with  the  inferior  and 
superior  trunks,  and  an  irregular  series,  further  apart,  connect 
the  dorsal  with  the  two  superior  trunks.  The  chylous  vessels 
as  in  the  ray  open  into  the  ductus  of  Cuvier. 

Sappey  found  lymphatic  glands  in  the  walls  of  the  digestive 
tract  and  on  the  hearts  of  the  ray,  dogfish  and  sturgeon. 

Mayer  (18)  in  a  most  extensive  monograph  on  the  peculiari- 
ties of  the  organs  of  circulation  in  Selachians  describes  these 
subcutaneous  vessels  in  Squatina,  Torpedo,  and  Raja  as  veins. 
On  pp.  339  and  340  he  states  that  when  a  young  ScylUum 
canicula  is  placed  in  an  aquarium,  that  the  vena  -postica  of  all 
the  vertical  fins  are  plainly  visible.  If  the  fish  is  excited  the 
blood  rapidly  disappears  from  these  veins,  but  returns  again 
after  a  brief  rest.  With  the  ordinary  swimming  back  and  forth 
the  blood  is  said  to  remain  in  the  fins.  Sometimes  no  fluid 
flowed  out  of  the  lateral  vein  after  cutting  it ;  consequently 
Mayer  reasons  because  a  trunk  is  bloodless  it  does  not  necessa- 
rily follow  that  it  is  a  lymphatic  vessel.  According  to  Mayer 
(pp.  366-7  and  9)  the  subcutaneous  veins  do  not  carry  pure 
blood,  but  rather  a  mixture  of  blood,  a  few  small  discs,  many 
leucocytes,  intermixed  with  a  fluid  resembling  chyle  ;  while  the 
intestinal  veins  commonly  contain  blood,  but  at  stated  times  chyle. 
Mayer  has  injected  the  sheaths  surrounding  the  intestinal  blood 
vessels  and  finds  the  chylous  system  of  vessels  as  observed  by 
Robin.  On  p.  368  he  severely  criticises  Sappey  for  not  being 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     89 

able  to  let  go  of  the  idea  that  a  fish  must  have  a  lymphatic  sys- 
tem ;  while  he  himself  is  so  impressed  with  the  uselessness  of 
such  a  system  to  a  fish,  that  it  almost  appears  to  him  as  if  it 
would  be  hateful  in  the  eyes  of  the  Lord  for  a  fish  to  possess  a 
lymphatic  system.  One  might  equally  well  apply  the  same 
line  of  reasoning  to  mammals. 

With  Raja  clavata  Mayer  found  the  lymphatic  hearts  of  Ley- 
dig  and  Sappey,  or  as  he  calls  them  sphincters,  very  abund- 
ant ;  while  with  their  close  relatives  they  were  often  absent.  He 
also  found  them  encircling  arteries,  and  hence  for  these  reasons 
was  not  willing  to  attribute  the  importance  to  them  that  Sappey 
did. 

In  the  trunk  region,  in  addition  to  the  caudal  vein  and  its  inter- 
costal branches,  Mayer  notes  (pp.  316-337)  not  fewer  than  four 
longitudinal  veins  that  have  no  counterpart  in  the  arterial  sys- 
tem. They  are  homologous  to  the  dorsal,  ventral,  and  lateral 
cutaneous  veins  of  Parker  and  the  corresponding  lymphatic 
trunks  of  Sappey.  In  addition  to  the  descriptions  given  these 
vessels  by  these  authors,  Mayer  finds  that  the  laterals  not  only 
terminate  cephalad  in  subscapular  reservoirs  that  empty  into  the 
cardinal  sinuses,  but  continue  cephalad  to  the  orbit,  where  they 
send  off  anastomosing  cross  branches  that  also  unite  with  the 
dorsal  vein.  Caudad  the  dorsal  vein  empties  into  a  lateral  and 
they,  at  the  origin  of  the  tail,  unite  with  the  ventrals,  which  are 
here  paired,  and  shortly  bend  dorsad  to  culminate  in  the  caudal 
vein.  The  two  forks  of  the  dorsal  that  encircle  the  dorsal  fins 
are  designated  by  Mayer  as  vence  circulares,  which  are  said  to 
receive  two  large  branches  from  each  fin.  One  or  two  vena 
postica  come  from  the  posterior  part  of  the  fin,  and  a  vena  pro- 
funda  arises  from  the  musculature  of  the  fin.  They  unite  in  a 
small  reservoir  at  the  base  of  the  fin,  which  communicates  with 
the  vena  circularis.  All  of  the  orifices  in  the  reservoir  are  said 
to  be  guarded  by  valves.  Also  all  of  the  venous  openings  into 
the  caudal  vein  are  likewise  protected  by  valves.  Certain  blood 
cavities  were  found  in  the  haemal  canal,  which  may  correspond 
to  the  haemal  lymphatic  trunk  of  the  bony  fishes. 

Neuville  (op.  cit.)  studied  in  detail  the  blood  vascular  supply  of 
the  viscera  in  Petromyzon  marimis  and  in  numerous  Selachians. 


90  ALLEN 

In  the  beginning  of  his  paper  he  gives  a  most  complete  historical 
sketch  of  all  the  work  done  on  the  circulatory  and  lymphatic 
systems  of  fishes,  and  contends  that  all  the  vessels  found  in  the 
digestive  tracts  of  the  Cyclostomes  and  Selachians  are  either 
arteries  or  veins  and  that  a  separate  chylous  system  does  not 
exist.  He,  however,  finds  a  double  venous  system  on  the  diges- 
tive tract  of  Acanthias  vulgaris;  one  of  which  is  the  portal  sys- 
tem, and  the  other  system,  which  is  figured  on  p.  92,  he 
recognizes  as  corresponding  to  the  descriptions  of  the  chylous 
system  as  given  by  Robin  and  the  older  authors.  Nevertheless 
he  considers  them  as  veins  for  the  following  reasons  :  First,  on 
p.  90,  he  has  found  the  sinus  5/0fl/<2£tf /  (Cisterne  de  Pecquet  of 
Fohmann)  to  be  full  of  blood.  Second,  on  p.  94,  he  finds  that 
upon  injecting  this  system  that  the  entire  portal  system  is  im- 
mediately filled.  According  to  Neuville  the  system  of  absorp- 
tion is  entirely  carried  on  by  the  veins  in  these  groups,  and  with 
the  Cyclostomes  he  finds  the  arrangement  of  the  veins  less  com- 
plex than  in  the  Selachians,  which  is  in  accord  with  their  less 
complicated  digestive  tract. 

A  year  later  Vialleton  (op.  ctt.}  takes  up  the  same  problem 
from  the  standpoint  of  the  digestive  tract  of  Torpedo,  and 
claims  that  Neuville  was  too  hasty  in  his  conclusions.  In  reply 
to  the  two  objections  raised  by  Neuville  as  to  this  system  of 
vessels  being  veins  rather  than  chylous,  Vialleton  says  (p.  382) 
in  answer  to  the  first  that  it  is  not  strange  to  find  blood  in  a 
lymphatic  trunk.  As  regards  the  second  he  states  (p.  383)  that 
Neuville  much  less  than  Mayer  has  not  attempted  a  micro- 
scopical study  of  these  vessels,  that  since  he  has  not  seen  the 
connections  of  the  superficial  canals  with  the  veins  he  does  not 
know  but  that  they  may  be  only  artifacts,  and  further  declares  that 
a  histological  investigation  revealed  the  fact  that  these  communi- 
cations were  found  to  be  caused  by  the  rupture  of  the  venous 
wall,  which  is  a  contact  wall  between  these  two  systems.  Vial- 
leton found  (pp.  452-3)  that  there  were  distinct  superficial  and 
profundus  lymphatic  networks  in  the  digestive  tract  of  Torpedo, 
which  could  readily  be  told  from  the  venous  capillaries  on 
account  of  the  form  of  its  network,  its  regular  caliber,  and 
greater  volume.  By  injecting  the  lymphatics  of  the  intestine 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     9! 

with  blue  and  the  veins  with  a  nitrate  of  silver  solution  it  was 
conclusively  proved  from  a  histological  standpoint  that  these 
two  systems  were  always  distinct,  often  running  side  by  side 
and  entwining,  but  never  anastomosing. 

Like  Neuville,  Vialleton  included  only  the  viscera  in  his  stu- 
dies and  devoted  the  first  part  of  his  work  to  a  most  excellent 
account  of  the  history  of  the  lymphatics  of  fishes.  In  review- 
ing Sappey's  memoir  (p.  392)  he  stated  that  the  numerous  anas- 
tomosing of  the  subcutaneous  lymphatics  with  the  veins,  and 
the  origin  of  certain  lymphatic  twigs  from  veins  leads  one  to  be- 
lieve that  the  vessels  described  by  Sappey  as  lymphatics  are 
veins.  It  should  be  remembered,  however,  that  Sappey  used 
mercury  for  his  injecting  mass ;  hence  it  would  not  be  surpris- 
ing if  these  connections  of  the  minute  lymphatics  with  the  veins, 
reported  by  Sappey  (p.  24)  in  the  abdominal  region,  are  arti- 
facts formed  by  the  extravasations  of  the  injecting  mass. 

Hopkins'  most  excellent  paper  on  Amia  (8)  is  to  my  knowl- 
edge the  only  work  that  has  appeared  on  the  Ganoids. 

He  finds  that  each  lateral  lymphatic  trunk  terminates  ante- 
riorly, in  front  of  the  pectoral  arch,  in  a  cephalic  sinus,  which 
extends  from  the  clavicle  into  the  base  of  the  cranium,  where  it 
could  be  traced  to  a  point  opposite  the  orbit.  About  i  cm. 
cephalad  of  the  clavicle  there  is  a  valve,  which  closes  an  open- 
ing that  leads  ventrad  into  the  jugular  vein.  Posteriorly  each 
lateral  trunk  ends  in  a  caudal  sinus,  which  is  located  under  the 
last  vertebrae.  Each  sinus  has  a  cephalic  connection  with  the 
caudal  vein,  the  orifice  being  guarded  by  a  valve,  and  there 
are  said  to  be  at  least  two  communications  with  its  fellow  sinus. 
The  dorsal  lymphatic  trunk  terminates  anteriorly  in  the  cephalic 
sinus,  and  posteriorly  into  one  of  the  laterals  after  the  latter 
bends  to  enter  the  caudal  sinus.  Hopkins  is  not  positive 
whether  this  trunk  bifurcates  posteriorly  with  each  fork  termin- 
ating in  one  of  the  laterals  or  not,  but  thinks  that  it  does.  Ac- 
cording to  the  writer  the  ventral  trunk  begins  in  the  tail  and 
communicates  through  a  cross  vessel  with  the  lateral  (Fig.  n, 
/).  It  collects  the  lymph  from  the  anal  and  the  ventrals,  and 
in  the  neighborhood  of  the  heart  it  forks,  the  two  branches 
merging  into  the  pericardial  sinus,  which  discharges  itself  into 


92  ALLEN 

the  cephalic  sinus  a  little  behind  the  jugular  opening.  A  large 
pectoral  sinus  is  said  to  lie  at  the  base  of  the  pectoral  fin,  which 
sends  off  branches  to  the  lateral  trunk  and  one  to  the  pericardial 
sinus.  The  termination  of  the  chylous  system  is  in  the  ductus 
of  Cuvier,  on  either  side  of  the  heart. 

On  p.  369  Hopkins  states  that:  "In  a  specimen  killed  by 
pithing,  the  cephalic  lymph  sinus  was  exposed  while  the  heart 
was  still  beating ;  the  veins  were  gorged  with  blood  but  the 
lymph  sinus  appeared  perfectly  clear  and  transparent,  and  at 
no  time  was  blood  found  in  the  lateral  vessels.  In  several  in- 
stances a  clear  fluid  was  seen  to  run  out  of  the  lateral  vessel, 
when  cut,  in  a  fresh  specimen." 

Were  not  constant  reference  to  this  paper  to  occur  in  the  text 
a  far  more  complete  report  of  it  should  be  given  here. 

The  latest  work  bearing  on  this  subject  is  by  Jossifoo  (op.  ctt.). 
He  takes  up  in  detail  the  lymphatics  in  Conger  and  Anguilla. 
The  main  ducts  of  Conger  (pp.  414-420)  follow  the  vertebral 
column  from  the  tail  to  the  skull.  In  the  caudal  region  the 
principal  trunk  (L.  Caud,  in  PL  12)  lies  in  the  haemal  canal, 
directly  below  the  caudal  vein.  When  the  thorax  is  reached  it 
divides,  forming  the  two  perivertebral  lymphatic  trunks  (R.  and 
L.Pr.S.),  which  continue  cephalad  along  the  sides  of  the  verte- 
bral column.  At  the  level  of  the  fifteenth  and  sixteenth  verte- 
bras the  right  trunk  receives  the  lacteal  canals  (D.  Ch.)  from  the 
viscera,  and  upon  reaching  the  fourth  vertebra  a  transverse 
vessel  of  considerable  size  (La.)  connects  the  two  trunks.  At 
the  base  of  the  cranium  each  perivertebral  trunk  empties  into  a 
cephalic  sinus  (S.C.),  which  communicates  with  the  jugular  as 
it  leaves  the  skull,  and  both  the  orifices  of  the  vein  and  the  lym- 
phatic trunk  are  said  to  be  guarded  by  semilunar  valves.  This 
sinus  is  so  situated  between  the  superior  maxilla  and  the  tem- 
poral bone  that  the  act  of  respiration  must  necessarily  dilate  and 
contract  it.  In  Anguilla  the  author  (p.  418)  states  that  upon 
injecting  the  perivertebral  trunks  one  invariably  fills  the  bran- 
chial lymphatic  sinuses,  situated  outside  the  vertebral  column  be- 
tween the  gills.  These  sinuses  communicate  with  the  periverte- 
bral trunks  and  serve  as  reservoirs  to  the  lymphatic  vessels 
arising  from  the  mucosa  of  the  branchial  arches.  A  pulsating 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     93 

lymphatic  heart  was  found  in  the  tail  of  Anguilla^  but  its  con- 
nections with  the  lymphatic  system  were  not  made  clear.  A 
specimen  of  Anguilla  was  said  to  have  lived  several  days  in  an 
aquarium  after  its  tail  had  been  cut  off,  without  seeming  to 
suffer  from  the  operation. 

From  what  we  know  of  the  development  of  the  lymphatics  in 
mammals  *  it  would  not  be  surprising  to  find  in  the  embryos  of 
the  lower  forms,  if  not  in  the  adults  also,  even  closer  relation- 
ships between  these  two  systems.  For  example,  it  might  be 
possible  to  find  a  vessel  that  functioned  both  as  a  vein  and  a 
lymphatic  trunk,  and,  again,  an  homologous  vessel  or  system 
of  vessels  might  exist,  which  functioned  as  veins  in  the  more 
generalized  forms,  but  which  had  their  exact  counterpart  in 
lymphatic  canals  in  the  higher  or  more  specialized  forms.  It 
is  very  evident  from  the  above  discussion  that  the  last  word  has 
not  been  said  on  this  subject.  What  is  most  needed  is  not  more 
generalizations,  but  more  anatomical  and  embryological  data  on 
many  different  groups,  and  especially  in  the  Cyclosomes.  It  is 
not  therefore  my  intention  to  make  what  might  be  considered 
a  dogmatic  statement  as  to  whether  these  subcutaneous  vessels 
in  the  Ganoids  are  veins  or  lymphatics.  The  chief  aim  will  be  to 
give  an  accurate  description  of  the  distribution  of  these  vessels. 
They  will,  however,  be  described  as  lymphatics  because  the 
balance  of  evidence  (such  as  size  and  arrangement  of  capillaries, 
and  the  fact  that  except  in  the  branchial  region  the  main  ducts 
in  the  head  region  always  accompany  venous  trunks),  seems 
to  warrant  thjs  view.  Yet,  on  the  contrary,  it  must  be  admitted 
that  if  these  vessels  are  termed  lymphatics  in  the  branchial  region 
no  corresponding  nutrient  branchial  veins  were  found ;  further, 

!In  an  especially  interesting  paper  Miss.  Sabin  (27)  found  a  stage  in  the 
embryo  pig  that  about  corresponded  with  the  lymphatic  system  of  the  adult  frog. 
Here  there  were  two  cervical  hearts  or  sacs  that  received  the  lymph  from  the  neck 
region  and  emptied  into  the  cardinal  vein  at  its  junction  with  the  subclavian,  the 
opening  being  guarded  by  a  valve.  Similar  posterior  hearts  were  found  to  dis- 
charge themselves  in  the  common  vein  formed  by  the  union  of  the  sciatic  with 
the  femoral,  and  their  orifices  were  likewise  said  to  be  protected  by  valves.  It 
was  not  until  considerable  later  that  the  thoracic  duct  and  the  right  lymphatic 
duct  were  formed  from  the  anterior  heart.  To  begin  with,  the  lymphatic  system 
of  the  pig  is  said  to  have  its  origin  from  two  blind  ducts  that  arise  from  the  car- 
dinal at  its  junction  with  the  subclavian. 


yq  ALLEN 

the  branchial  trunks  were  always  filled  with  red  corpuscles,  and 
unquestionably  terminated  in  and  apparently  formed  the  prin- 
cipal supply  for  the  so-called  inferior  jugular  vein. 

II.    DISTRIBUTION    OF    THE    SUBCUTANEOUS    VESSELS    IN 
POLYODON. 

The  distribution  of  the  subcutaneous  vessels  in  the  head  region 
of  Polyodon,  which  is  a  cartilaginous  Ganoid,  and  Lepisosteus, 
a  bony  Ganoid,  admits  of  so  little  comparison,  that  it  seems 
advisable  to  consider  this  system  of  vessels  separately  in  each 
case,  rather  than  to  take  them  up  together  in  a  comparative  way. 
In  the  former  these  vessels,  in  some  respects,  agree  more  closely 
with  the  Selachians,  while  in  the  latter  they  are  more  like  the 
Teleosts. 

i.    Cephalic  Sinuses  and  their  Connections. 

What  has  been  designated  as  the  cephalic  sinuses  (Fig.  i, 
Ceph.S.}  in  Polyodon  are  two  rectangular-shaped  reservoirs, 
which  are  symmetrically  placed  on  either  side  of  the  body, 
directly  mesad  of  the  supra-clavicles,  and  only  a  little  below 
the  level  of  the  post-temporals.  In  the  specimen  from  which 
Fig.  i  was  drawn  their  dimensions  were  about  40  by  18  mm. 
With  the  exception  of  the  posterior-ventral  corner,  each  corner 
of  a  cephalic  sinus  has  an  orifice.  The  trunk  leading  into  the 
posterior  dorsal  opening  is  the  lateral  lymphatic  trunk  (Fig.  i, 
L.L.T.).  In  the  thoracic  region  the  lateral  trunks  were  the 
only  subcutaneous  vessels  found  ;  though  both  dorsal  and  ven- 
tral trunks  were  observed  farther  caudad.  Very,  singular  in 
Polyodon  the  lateral  trunks  have  an  extremely  small  diameter, 
but  little,  if  any,  greater  than  the  lateral  line  canals.  Fortu- 
nately, however,  they  increase  in  caliber  upon  approaching  the 
cephalic  sinuses ;  otherwise  it  would  be  impossible  to  inject 
them,  except  with  a  very  fine  hypodermic  needle.  What  are 
represented  as  the  cephalic  lymphatic  trunks  (Fig.  i,  Ceph.L. 
T.)  terminate  in  the  anterior  dorsal  corners  of  these  sinuses,  and 
in  one  way  or  another  these  great  canals  drain  the  entire  head 
region.  The  openings  from  the  anterior  ventral  corners  lead 
into  papillae  (Fig.  i,  V),  which  discharge  themselves  ventrad 
into  the  jugulars ;  either  at  the  angles  of  their  great  bends  in 
front  of  the  pectoral  arches,  or  a  little  below. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     95 

So  far  as  could  be  ascertained  by  dissections  and  injections 
no  valves  were  found  at  the  entrance  of  either  the  lateral  or 
cephalic  trunks  in  the  cephalic  sinus,  or  at  the  opening  of  the 
latter  into  the  jugular  vein,  but  as  none  of  these  orifices  was 
large  a  histological  study  might  have  revealed  their  presence. 
Still,  however,  when  the  blood  vessels  were  injected  with  a  blue 
mass,  the  cephalic  lymphatic  trunks  were  invariably  filled  from 
either  the  lymphatic  sinus  or  the  inferior  jugular  connections 
or  through  both,  and  when  the  blue  was  allowed  partially  to 
solidify  before  the  lateral  trunk  was  injected  with  the  yellow ;  it 
was  found,  upon  dissection,  that  the  yellow  had  forced  back  the 
blue  a  short  distance  in  both  the  jugular  and  in  the  cephalic 
trunk,  but  none  of  it  had  reached  the  inferior  jugular,  showing 
conclusively  that  if  there  were  valves  at  the  entrance  of  the 
cephalic  trunk  opening  into  the  cephalic  sinus  that  after  death, 
at  least,  they  are  unable  to  repel  an  injecting  mass,  when  only 
a  slight  pressure  is  applied. 

It  will  be  readily  noted  that  the  cephalic  sinus  of  Polyodon 
corresponds  exactly  in  position  to  a  similar  reservoir  described 
by  Vogt  (i,  pp.  137-8)  in  the  salmon,  but  its  shape  and  mode 
of  communications  are  very  different.  With  the  salmon  this 
sinus  is  said  to  empty  into  the  ductus  of  Cuvier/and  in  addition 
to  receiving  the  lateral  trunk  it  collects  three  mucous  canals,  as 
they  are  called,  from  the  head  region.  The  first  of  these  canals 
is  represented  as  arising  at  the  origin  of  the  temporal  (pterotic) 
crest  from  two  branches  coming  from  the  facial  region.  The 
second  of  these  canals  is  portrayed  (PI.  L,  Fig.  i,  63)  as  hav- 
ing its  source  from  six  branches  ;  one  large  and  one  small  vessel 
coming  from  each  of  the  first  three  branchial  arches.  The 
smaller  branch  is  said  to  have  its  origin  from  the  filaments ; 
while  the  larger  branch  is  a  more  superficial  trunk,  that  con- 
tinues ventrad  along  the  surface  of  the  arch  to  anastomose  with 
the  vein  of  Duvernoy  (inferior  jugular).  The  third  canal  comes 
from  a  common  reservoir  situated  near  the  fourth  vertebra, 
which  is  described  as  receiving  a  trunk  from  the  fourth  branchial 
arch,  and  one  from  the  median  part  of  the  body  that  also  col- 
lects the  chylous  duct. 

Hopkins'  cephalic  sinus  in  Amia  (8,  p.  371  and  Fig.  10,  b) 

Proc.  Wash.  Acad.  Sci.,  July,  1907. 


96  ALLEN 

is  located  a  little  further  cephalad  than  the  similar  reservoir  in 
Polyodon^  being  situated  entirely  in  front  of  the  pectoral  arch. 
The  writer  observed  that  this  sinus  continued  cephalad  in  the 
cranium  to  a  point  about  opposite  the  orbit.  As  in  Polyodon  it 
is  discharged  into  the  jugular,  but  the  orifice  is  said  to  be 
guarded  by  a  valve  opening  into  the  vein.  No  cephalic  trunks 
were  represented  as  emptying  into  the  cephalic  sinus,  but  in 
addition  to  the  lateral  trunk  a  fork  of  the  dorsal  is  said  to  have 
its  termination  in  each. 

Cephalic  lymphatic  trunk  (Figs,  i,  2  and  3,  Ceph.L.T.). — 
This  is  the  largest  and  undoubtedly  one  of  the  most  important 
of  the  lymphatic  canals  in  Polyodon.  In  a  7<>pound  specimen 
it  had  a  length  of  12  cm.,  extending  from  the  base  of  the  skull 
to  the  pectoral  arch,  and  connecting  the  so-called  hyo-opercu- 
laris  sinus  (Figs,  i,  2  and  3,  Hyo.O.S.}  with  the  cephalic  sinus. 
Its  caliber  if  anything  exceeded  the  jugular  vein,  but  pos- 
teriorly it  rapidly  tapers  down  into  a  papilla  preparatory  to 
emptying  into  the  cephalic  sinus.  In  position  it  follows  along 
directly  above  the  jugular  vein,  about  midway  between  the 
pterotic  crest  and  the  gills.  The  cephalic  trunk  is  strictly  a 
superficial  canal,  being  separated  from  the  branchial  cavity  by 
a  thick  skin  that  bears  numerous  leaf-like  papilla ;  it  is  sur- 
rounded by  a  tough  connective  tissue,  and  cephalad  a  gland-like 
body,  which  I  take  to  be  the  thymus,  lies  between  it  and  the 
skin.  The  integment  of  this  whole  region  contains  a  typical 
lymphatic  network  (Fig.  i,  L.N.(i)),  which  is  collected  mesad 
by  larger  vessels  that  apparently  discharge  themselves  into  the 
dorsal  end  of  the  hyo-opercularis  sinus  rather  than  into  this 
trunk.  When  the  hyo-opercularis  sinus  is  reached  the  cephalic 
trunk  bifurcates :  the  dorsal  fork  communicates  with  the  hyo- 
opercularis  sinus  from  the  rear  and  behind  (Figs,  i  and  2, 
C.L.T.O.\  while  the  ventral  fork  runs  parallel,  but  mesad,  of 
the  hyo-opercularis  sinus  for  a  short  distance.  In  this  region 
the  ventral  fork  receives  at  least  two  branches  coming  up  along 
the  inner  surface  of  the  branchial  levator  and  the  pharyngo 
clavicularis  muscles.  Corresponding  venous  trunks  (Fig.  i) 
followed  the  course  of  these  lymphatic  branches  and  terminated 
in  the  jugular.  Frequently  as  is  shown  in  Fig.  i  a  valve  is 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     97 

found  in  the  hyo-opercularis  fork  of  the  cephalic  trunk,  at  its 
junction  with  the  ventral  fork,  which  opens  towards  the  cephalic 
sinus,  but  from  its  size  one  would  not  expect  it  capable  of  en- 
tirely closing  the  opening.  A  little  posterior  to  the  division  of 
the  cephalic  canal  a  combined  trunk  formed  from  the  fusion  of 
the  last  three  branchial  lymphatic  vessels  (Fig.  i,  X)  is  received 
from  below,  which  will  be  described  in  detail  later  on  under  the 
head  of  the  branchial  lymphatic  trunks. 

What  is  termed  the  fericardial  lymphatic  trunk  (Fig.  I, 
Per.L.  T.}  corresponds  somewhat  in  position  to  the  pericardia! 
sinus  of  Leftsosteus  and  the  Teleosts,  without  presenting  any- 
thing like  a  sinus-like  appearance.  It  is  simply  a  canal  running 
along  in  front  of  the  pectoral  arch  in  the  connective  tissue  that 
surrounds  the  precava.  Immediately  after  crossing  the  commu- 
nicating vessel  of  the  cephalic  sinus  with  the  jugular  it  makes  a 
dorsal  curve  to  culminate  in  the  cephalic  trunk,  near  its  union 
with  the  cephalic  sinus. 

In  several  different  specimens  of  Polyodon  blood  was  removed 
with  a  pipette  from  the  jugular  and  injected  into  a  vial  contain- 
ing alcohol ;  likewise  some  fluid  from  the  cephalic  lymphatic 
trunk  was  placed  in  a  second  vial  containing  alcohol.  Upon 
settling,  the  corpuscles  from  the  vein  had  a  distinct  brown  or 
reddish  color ;  while  those  from  the  cephalic  trunk  were  prac- 
tically colorless.  Microscopic  sections  of  the  two  trunks  reveal 
the  walls  to  be  structurally  about  the  same.  (Compare  Fig. 
22  with  23.)  Both  are  composed  mainly  of  fibrous  connective 
tissue,  with  scattering  smooth  muscle  fibers,  and  both  have  nu- 
merous papilla  (P),  which  extend  some  little  distance  into  the 
trunk  and  may  to  some  extent  function  as  valves.  The  greatest 
difference  between  these  two  vessels  is  in  relation  to  their  con- 
tents. The  cephalic  canal  is  filled  with  leucocytes  and  a  few 
scattering  red  corpuscles,  while  in  the  jugular  the  red  corpuscles 
greatly  predominate  ;  there  being,  however,  in  the  latter  a  greater 
proportion  of  white  corpuscles  than  would  be  found  in  the  mes- 
enteric  or  inferior  jugular  veins.  With  the  cephalic  trunk  in 
the  region  covered  by  the  field  of  Fig.  22  the  red  corpuscles 
were  to  the  white  as  8  is  to  153  ;  while  with  the  jugular  in  the 
area  covered  by  Fig.  23  the  ratio  of  red  to  white  was  36  to 


p8  ALLEN 

19.  Directly  laterad  of  the  cephalic  canal,  in  this  region,  there 
is  a  gland-like  body,  the  thymus,  which  is  completely  rilled  with 
leucocytes,  and  in  places  one  can  see  them  transuding  through 
the  walls  of  the  lymphatic  duct. 

As  regards  its  mode  of  origin,  position,  and  point  of  termina- 
tion the  cephalic  sinus  of  Polyodon  corresponds  somewhat  with 
the  second  trunk  described  by  Vogt  in  the  salmon  as  emptying 
into  the  common  reservoir  (i,  pp.  137-8  and  PL  L,  Fig.  i,  63). 
Its  position  is  also  similar  to  Sappey's  sinus  curviligne  in  the 
skate  (25,  p.  20,  and  PL  5,  Fig.  i,  5). 

Hyo-opercularis  sinus  (Figs,  i,  2,  and  3,  Hyo.O.S.), — The 
sinus  so  designated  is  but  little  if  any  greater  in  diameter  than 
the  cephalic  trunk ;  it  is  situated  rather  obliquely  at  the  base  of 
the  skull,  and  is  distinctly  a  superficial  duct,  which  at  one  point 
crosses  laterad  of  the  jugular.  Its  length  is  apparently  about 
the  same  in  a  25-pound  specimen  as  in  a  7o-pound  one. 
Dorsad  it  receives  a  short  vessel  that  collects  trie  rich  network 
(Fig.  i,  JL.N.(i))  from  the  skin  and  connective  tissue  in  the 
region  of  the  cephalic  trunk.  Its  mode  of  connection  or  termi- 
nation in  the  cephalic  trunk  has  already  been  described.  In  one 
way  or  another  it  receives  both  forks  of  the_/£r5/  branchial  lyni- 
fhatic  trunk  (Figs,  i,  2,  and  3,  £r.L.T.(if)  and  (i")),  which 
will  be  referred  to  in  detail  later  on  under  the  head  of  the 
branchial  lymphatics.  Laterad  and  ventrad  it  receives,  or  vir- 
tually is  continuous  with,  the  so-called  hyo-opercularis  lymphatic 
trunk)  and,  as  shown  in  Fig.  i,  a  valve  is  often  present  at  the 
junction  of  the  two. 

Tracing  this  important  canal  (Figs,  i,  2,  3,  and  4,  Hyo. 
O.L.T.)  backward,  it  was  found  immediately  before  making  a 
sharp  curve  caudad  in  order  to  pass  along  the  outer  surface  of 
the  retractor  hyomandibularis  muscle,  a  little  above  the  hyo- 
mandibular,  that  it  was  joined  by  a  significant  facial  lymphatic 
trunk  (Figs,  i,  2,  and  3,  F.L.T.}.  Throughout  its  entire 
course  the  hyo-opercularis  is  distinctly  a  superficial  canal,  lying 
directly  beneath  the  skin ;  it  has  its  beginning  from  the  hyoid 
arch  and  the  opercle,  and  collects  a  network  (Fig.  i,  Z.7Vr.(3)) 
from  the  membranes  and  connective  tissue  of  hyomandibular 
and  its  retractor  muscle ;  this  network  communicates  below 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS     99 

with  what  is  designated  as  the  anterior  facial  lymphatic  trunk 
(Fig.  1,7^.^.7^(1)).  A  cut  through  the  spiracle  region  near  the 
termination  of  hyo-opercularis  trunk  in  the  sinus  shows  that  this 
canal  is  accompanied,  more  profundously,  by  a  corresponding 
hyo-opercularis  artery  and  vein.  All  of  these  vessels  are  en- 
closed in  a  fatty  connective  tissue,  and  even  in  uninjected  spec- 
imens they  are  readily  distinguishable.  The  lymphatic  trunk  is 
the  most  superficial  and  has  by  far  the  greatest  caliber ;  no  dis- 
tinct walls  were  visible  to  the  eye,  and  it  appeared  to  be  simply 
a  regular  cavity  in  the  connective  tissue,  that  increased  in  den- 
sity in  the  neighborhood  of  the  canal.  A  little  mesad  comes 
the  vein,  having  visible  walls,  but  with  a  caliber  hardly  half 
that  of  the  lymphatic  trunk.  The  artery,  which  is  by  far  the 
smallest  of  the  three,  is  some  little  deeper,  and  is  characterized 
by  very  thick  and  well-defined  walls.  A  short  distance  behind 
the  anterior  bend  the  hyo-opercularis  trunk  receives  a  large 
dorsal  branch  (Fig.  4,  Uyo.O.L.T.(i)},  which  takes  its  origin 
from  the  outer  dorsal  surface  of  the  retractor  hyomandibularis 
muscle.  At  this  point  the  hyo-opercularis  artery  and  vein  follow 
the  hyomandibular  rather  than  the  lymphatic  trunk,  yet  each 
sends  off  a  superficial  branch  (Fig.  4,  ffyo.O.A.(i)  and 
Hyo.O.  F'.(i))  that  crosses  mesad  of  the  lymphatic  trunk,  and 
which  separates  into  two  branches  that  follow  the  main  hyo- 
opercularis  lymphatic  trunk  and  its  dorsal  branch.  So  that  in 
this  region,  each  lymphatic  canal  is  accompanied  by  an  artery 
and  a  vein. 

Figures  24  to  26  represent  microscopic  sections  of  the  hyo- 
opercularis  lymphatic  trunk,  artery  and  vein.  Except  for  the 
papilla,  Fig.  24,  P.,  in  the  lymphatic  trunk,  there  is  but  little 
difference  between  the  structure  of  the  lymphatic  trunk  and  the 
vein,  and  both  resemble  the  jugular  and  the  cephalic  lymphatic 
canal.  When  the  hyo-opercularis  lymphatic  trunk  was  slit  in  a 
living  specimen  it  was  found  to  be  practically  empty,  and  sec- 
tions show  it  to  be  almost  destitute  of  corpuscles.  Fig.  24 
is  taken  from  a  very  favorable  section,  and  some  of  the  few 
corpuscles  portrayed  here  may  have  been  shaken  out  from  the 
meshes  of  the  walls  during  the  process  of  staining,  but  as  the 
section  stands  it  shows  that  the  white  corpuscles  far  exceed  the 


100  ALLEN 

red,  the  ratio  being  28  to  2.  Fig.  26  represents  the  corpuscles 
as  also  being  very  scarce  in  the  vein,  but  here  the  red  predomi- 
nate, the  ratio  being  9  to  2  ;  while  in  the  artery  the  corpuscles 
are  abundant,  the  ratio  of  red  to  white  being  as  36  is  to  8, 
which,  however,  is  a  striking  number  of  white  corpuscles  for 
an  artery.  In  the  artery  the  three  tunics  are  very  thick  and 
well  differentiated. 

Facial  Lymphatic  Trunks.  —  In  Polyodon  there  are  two 
such  canals,  on  either  side  of  the  body,  which  for  convenience 
sake  have  been  designated  as  the  facial  lymphatic  trunks  and 
the  anterior  facial  lymphatic  trunks. 

The  latter  trunks  (Fig.  i,  F.L.T.(i))  take  their  origin  from 
the  adipose  tissue  of  the  paddle,  in  front  of  the  nasal  sac. 
They  are  distinctly  subdermal  vessels,  being  situated  some 
little  distance  above  the  orbito-nasal  arteries  and  veins.  When 
the  level  of  the  posterior  border  of  the  nasal  sac  is  reached, 
each  trunk  bends  outward  and  downward,  to  pass  backward, 
superficially,  along  the  surface  of  the  adductor  mandibulae 
muscles.  In  the  region  of  the  spiracle  it  lies  immediately  in 
front  of  the  facialis  artery,  and  receives  a  rich  network  from 
above  (Fig.  I,  L.N.(2}),  that  passes  over  the  facialis  artery, 
nerve,  and  vein,  to  communicate  above  with  the  principal 
facialis  trunk.  Frequently  vessels  are  received,  which  collect 
the  network  arising  from  the  connective  tissue  that  envelops 
the  adductor  mandibulae  muscles ;  these  branches  ordinarily 
accompany  and  often  nearly  encircle  corresponding  blood  ves- 
sels. As  previously  stated  in  the  neighborhood  of  the  posterior 
extremity  of  the  premaxilla,  branches  are  received,  that  have 
their  source  from  a  rich  network  above  (Fig.  i,  L,.JV.(^  )), 
which  passes  over  the  hyomandibular  and  its  retractor  muscle 
to  communicate  with  similar  branches  that  end  in  the  hyo- 
opercularis  lymphatic  trunk. 

In  connection  with  the  anterior  facial  lymphatic  trunk  it  was 
just  noted  that  the  main  facial  lymphatic  trunk  (Figs.  1,2,  and 
3,  F.L.  T.)  gathered  a  rich  network  in  the  region  of  the  spiracle 
that  came  from  the  facialis  vein,  nerve,  and  artery,  and  was 
also  in  communication  with  the  anterior  facial  trunk.  The 
lymphatic  canal  thus  formed  follows  up  along  the  dorsal  surface 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    IOI 

of  the  facialis  vein,  and  when  the  external  carotid  artery  (Fig. 
i,  JE.Car.A.)  is  reached,  passes  mesad  with  it  in  crossing 
under  the  external  jugular  vein  (Fig.  i,  E.J.  F.),  and  then 
continues  caudad  a  short  distance,  still  mesad  of  the  artery. 
From  here  on,  instead  of  passing  ventrad  and  mesad  with  the 
external  carotid,  it  continues  caudad  on  practically  the  same 
level,  directly  mesad  of  the  external  jugular  and  above  the  hyo- 
opercularis  artery.1  In  this  locality,  which  is  about  opposite 
the  auditory  capsule  and  a  little  above  the  spiracle,  the  facial 
trunk  collects  a  very  rich  network  from  the  surface  of  the  ex- 
ternal jugular  and  the  hyo-opercularis  artery.  In  company 
with  the  hyo-opercularis  vein  (Fig.  i,  Hyo.O.  V.)  this  trunk 
bends  outward  at  right  angles.  In  Fig.  i  it  passes  between 
the  external  jugular  and  the  hyo-opercularis  artery,  following 
for  a  short  distance  below  and  in  front  of  the  hyo-opercularis 
vein,  and  then  bends  at  right  angles,  crossing  under  the  vein 
to  terminate  in  the  hyo-opercularis  lymphatic  trunk,  at  the  point 
where  it  becomes  the  hyo-opercularis  sinus.  In  Fig.  2  the 
facial  lymphatic  trunk  after  crossing  under  the  external  jugular, 
followed  below  the  hyo-opercularis  vein  for  a  very  short  dis- 
tance, before  curving,  to  culminate  in  the  hyo-opercularis 
trunk;  while  in  Fig.  3,  which  is  from  the  right  side  of  the 
same  specimen  as  Fig.  2,  the  facial  trunk  after  coming  out 
from  under  the  external  jugular,  nearly  encircles  the  hyo-opercu- 
laris vein,  before  emptying  into  the  hyo-opercularis  trunk. 

2.  Branchial  Lymphatics  (Nutrient  Branchial  Veins?). 

These  vessels  present  the  most  difficult  proposition  found  in 
Polyodon;  both  in  regard  to  tracing  out  their  distribution,  and 
in  determining  whether  they  are  veins  or  lymphatics,  or  a  com- 
mon system  that  may  function  for  both.  In  brief,  each  branchial 
arch  possesses  two  main  canals  ;  one  of  which  travels  along  the 
outer  and  inner  surface  of  the  arch ;  while  the  other  is  for  the 
most  part  confined  to  the  filaments,  following  along  between  the 
two  rows  or  hemibranchs,  with  the  efferent  branchial  artery, 

'This  artery  (Fig.  i,  Hyo.O.A.)  is  a  large  branch  of  the  external  carotid,  that 
for  a  short  distance  runs  caudad  with  the  external  jugular,  before  bearing  off 
obliquely  to  the  hyoidean  region. 


IO2  ALLEN 

but  distad  of  it.  The  latter  is  undoubtedly  the  principal  trunk, 
for  it  often  receives  the  former,  and  it  is  collected  above  by  either 
the  hyo-opercularis  sinus  or  the  cephalic  trunk,  and  below  by 
the  inferior  jugular.  Considerable  variation,  however,  is  shown 
in  both  the  dorsal  and  ventral  endings,  and  as  many  deviations 
are  to  be  found  on  the  opposite  sides  of  the  same  specimen  as 
on  the  same  sides  of  different  specimens.  Both  the  branchial 
trunks  and  the  branchial  arch  trunks  are  connected  by  a  very 
coarse  network  of  capillaries,  which  are  distinctly  lymphatic  in 
the  character  of  their  meshes.  Transverse  sections  through  the 
branchial  trunk  disclosed  it  to  be  full  of  red  corpuscles,  but  at 
no  point  was  a  definite  peripheral  connection  between  a  nutrient 
branchial  artery  established ;  although  at  several  places  hypo- 
thetical communications  might  occur. 

The  distribution  of  these  branchial  canals  is  practically  the 
same  for  the  first  three  arches  ;  hence  a  description  of  the  first 
arch  of  a  7o-pound  Polyodon,  as  shown  by  Fig.  17  will  answer 
for  all.  As  stated  above  the  main  branchial  lymphatic  trunk 
(nutrient  branchial  vein  f)  (Br.L.  T.)  travels  in  the  connective 
tissue,  midway  between  the  two  rows  of  filaments,  parallel  with, 
but  distad  of,  the  efferent  branchial  artery.  For  every  pair  of 
branchial  filaments,  a  rather  large  filament  lymphatic  trtmk 
(nutrient  vein?)  (Figs.  17,  18,  19,  and  27,  Fil.L.T.)  is  re- 
ceived from  the  connecting  tissue  lying  between  the  two  rows 
of  filaments.  A  cross-section  through  these  filaments  (Fig. 
27)  reveals  the  fact  that  these  branches  do  not  lie  opposite  each 
pair  of  filaments  as  the  two  corresponding  afferent  filament 
arteries  do  (Figs.  17  and  27,  A.Ftl.A.},  but  rather  about 
midway  in  the  space  separating  one  pair  of  filaments  from  the 
next,  and  Fig.  27  represents  each  of  these  filament  vessels  as 
being  about  equidistant  from  four  afferent  filament  arteries. 
Numerous  transverse  filament  lymphatic  vessels  (nutrient  veins  f) 
(Figs.  18  and  19,  Tr.F.L.  V.)  entwine  in  various  ways  with  the 
roots  from  which  the  corresponding  afferent  filament  transverse 
arteries  (Fig.  18,  A.F.Tr.A.)  take  their  origin,  and  form  a  very 
coarse  plexus-like  network  between  them.  These  vessels  col- 
lect a  very  rich  network  from  the  outer  surface  of  the  filament 
(Fig.  19,  T^'/.Z.TV^.),  which  in  the  region  of  the  respiratory  septa 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    IO3 

have  a  somewhat  rectangular  arrangement.  Certain  twigs  tra- 
verse the  superficial  layer  of  the  filament,  opposite  to  and  parallel 
with  the  spaces  separating  the  septa,  and  these  are  connected  by 
transverse  branches.  This  coarse  network  cannot  be  confused 
with  the  very  fine  respiratory  network  (Fig.  18,  Res.N.) ;  for  the 
latter  is  more  profundus,  being  confined  to  planes  or  septa, 
which  are  at  right  angles  to  the  so-called  lymphatic  network. 
With  a  magnification  of  450  diameters  (Fig.  iSa)  the  meshes  of 
the  respiratory  network  are  not  as  large  as  the  meshes  of  the 
lymphatic  network  as  viewed  with  a  magnification  of  50  diame- 
ters (Fig.  19) ;  hence  the  caliber  of  the  respiratory  capillaries  is 
almost  infinitesimal  when  compared  to  the  lymphatics.  After 
leaving  the  area  of  the  respiratory  septa,  which  is  toward  the 
outer  edge  of  the  filament,  the  lymphatic  network  assumes  a 
somewhat  different  character ;  here,  as  is  shown  in  the  lower 
part  of  Fig.  19,  the  meshes  become  crowded  closer  together ; 
while  on  the  outer  edge  of  the  filament,  in  the  region  of  the 
efferent  filament  artery,  the  meshes  become  elongated  in  the 
direction  of  the  artery,  which  is  exactly  at  right  angles  to  their 
greatest  length  in  crossing  the  filament.  An  examination  of 
the  basal  portion  of  the  filaments  and  the  membranes  overlying 
the  efferent  branchial  artery  with  a  lens  (Fig.  17),  or  better  still 
a  microscopic  preparation  of  this  region  (Fig.  20),  discloses  the 
fact  that  the  lymphatic  network  of  the  branchial  filaments  are 
continuous  with  a  similar  network  found  on  the  outer  and  inner 
surfaces  of  the  branchial  arch  (Figs.  17  and  20,  Br.A.L.N.}. 
Branchial  Arch  Lymphatics  (Nutrient  Veins  ?).  —  One  of 
these  vessels  (Fig.  17,  Br.A.L.  T.)  runs  along  the  inner  surface 
of  each  arch,  near  its  inner  margin.  It  receives  numerous 
radiating  branches,  which  collect  an  extremely  rich  network 
(Fig.  17,  Br.A.L.N.}  that  lies  in  the  deeper  membranes  and 
connective  tissue  lining  the  arch,  and  which  is  distinctly  lym- 
phatic in  the  character  of  its  meshes.  This  trunk  also  receives 
large  accessory  branches  that  gather  a  similar  network  from  the 
other  or  outer  side  of  the  arch.  So  fine  is  this  network  that  its 
meshes  cannot  be  seen  without  the  aid  of  a  lens.  At  various 
intervals  delicate  branches  could  be  traced  to  the  outer  mem- 
brane, where  they  collect  an  extremely  minute  capillary  net- 


104 


ALLEN 


work ;  so  that  each  branchial  arch  would  have  a  minute  capil- 
lary network  overlying  and  being  connected  with  a  more 
profundus  and  coarser  network.  Whether  this  outer  capil- 
lary network  was  also  in  communication  with  the  branchial 
arch  arteries  I  am  unable  to  state,  any  more  than  to  say  that 
no  connections  were  found.  A  large  number  of  small  vessels 
were  received  from  the  gillrakers,  the  common  arrangement 
being  that  two  minute  branches  followed  along  the  opposite 
surfaces  of  two  neighboring  gillrakers,  collecting  a  minute 
network  (Fig.  17,  G.R.L.N.)  found  in  the  membrane  joining 
the  two,  and  uniting  at  the  bases  of  the  gillrakers  to  form  a 
slender  twig,  which  terminates  in  that  porion  of  the  branchial 
arch  lymphatic  network,  overlying  the  efferent  branchial  artery 
(Fig.  17,  Br.A.L.N.}. 

In  the  specimen  from  which  Fig.  17  was  drawn  the  arterial 
system  was  first  filled  with  a  blue  mass,  and  afterward  the  sub- 
cutaneous system  was  injected  with  the  yellow  from  the  cephalic 
trunk.  In  certain  areas,  the  minute  capillary  network  found 
in  the  outer  membrane  covering  a  branchial  arch  was  colored 
yellow  and  in  other  regions  blue ;  similar  colored  areas  were 
also  found  in  the  more  profundus  network,  and  in  the  superfi- 
cial network  of  the  branchial  filaments.  Other  places  also  could 
be  found  in  the  more  profundus  network  of  the  arch  and  the 
superficial  network  of  the  filaments,  which  were  colored  green, 
showing  that  the  two  injecting  masses  had  fused.  It  does  not, 
however,  necessarily  follow  from  the  above,  that  these  capillaries 
are  in  connection  with  arterial  twigs.  For  in  almost  every  case 
when  the  blood  vessels  were  first  injected,  the  cephalic  trunk, 
the  superficial  network  of  the  filaments,  and  the  profundus  net- 
work of  the  arch  were  found  to  be  filled ;  doubtless  through 
either  the  connection  of  the  jugular  with  the  cephalic  sinus  or 
the  inferior  jugular  with  the  branchial  lymphatic  trunks,  or 
through  both.  Since  the  profundus  network  of  a  branchial  arch 
was  found  to  be  in  communication  with  the  minute  superficial 
network,  it  is  natural  to  expect  that  the  mass  found  its  way  into 
this  network  after  this  manner,  rather  than  through  hypothetical 
arterial  connections,  which  I  have  never  been  able  to  find,  either 
from  dissection  or  a  microscopical  examination  ;  and  upon  inject- 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    IO5 

ing  the  cephalic  trunk  with  the  yellow  mass,  it  simply  pushed 
back  the  blue,  forming  the  conditions  described  above,  viz.,  of 
certain  areas  of  one  color  and  other  regions  of  a  mixture. 

Whether  these  conditions  were  obtained  after  this  manner  or 
were  brought  about  through  the  media  of  peripheral  communi- 
cations with  the  nutrient  arteries,  might  possibly  be  settled  by 
removing  a  branchial  arch  from  a  large  Polyodon,  and  after 
securely  ligaturing  both  ends  of  the  arch  proper,  plug  up  one 
end  of  the  so-called  branchial  lymphatic  trunk  and  inject  from 
the  other,  but  most  unfortunately,  however,  these  subcutaneous 
branchial  vessels  were  not  studied  with  any  detail,  until  after  I 
was  removed  some  2,000  miles  from  the  source  of  material. 
Except  for  the  fact  that  nutrient  arteries  were  found  on  the 
arch,  and  no  nutrient  veins  were  observed,  unless  the  so-called 
lymphatics  function  for  both  veins  and  lymphatics,  I  can  see 
no  reason  for  maintaintng  that  hypothetical  peripheral  connec- 
tions exist  between  the  nutrient  arteries  and  the  so-called  bran- 
chial lymphatics.  Certainly  the  methods  resorted  to  in  this  study 
do  not  justify  it ;  in  fact,  the  numerous  connections  with  the 
inferior  jugular  and  the  two  with  the  jugulars  rather  forbid  such 
a  view. 

A  point  slightly  favoring  the  hypothesis  that  the  branchial 
subcutaneous  vessels  function  as  veins,  is  the  fact,  that  a  sec- 
tion through  a  main  branchial  lymphatic  trunk  (Fig.  28)  always 
shows  a  predominance  of  red  corpuscles.  The  ratio  of  red  to 
white  is  37  to  22,  which,  however,  lacks  considerable  of  being 
so  overwhelming  as  one  would  expect  to  find  in  a  vein.  For 
example  in  the  inferior  jugular,  into  which  these  vessels  ter- 
minate ventrad,  the  ratio  of  red  to  white  is  about  12  to  i  and  in 
the  mesenteric  vein  one  has  to  look  some  time  to  find  a  leuco- 
cyte ;  while  in  the  cephalic  trunk,  into  which  these  vessels 
culminate  dorsad,  the  red  corpuscles  are  very  scarce,  the  ratio 
of  white  to  red  being  153  to  8.  Hence  from  purely  histological 
grounds  one  might  infer  that  the  branchial  lymphatic  trunks 
discharged  themselves  mainly  into  the  inferior  jugular,  but  the 
fact  that  none  of  the  branchial  arch  trunks  terminates  in  the  in- 
ferior jugular,  while  some  of  them  do  empty  directly  into  the 
cephalic  trunk  ;  and  the  additional  observation  that  the  branchial 


106  ALLEN 

lymphatic  openings  into  the  hyo-opercularis  sinus  and  the 
cephalic  trunk  are  larger  than  those  into  the  inferior  jugular, 
barely  make  this  view  even  tenable. 

Respiratory  and  Nutrient  Branchial  Arteries. — These  vessels 
hold  such  an  intimate  relationship  with  the  so-called  branchial 
lymphatic  system,  and  are  so  different  from  the  similar  arteries 
found  in  bony  fishes,  that  a  brief  description  of  some  kind  seems 
to  be  called  for. 

With  the  exception  of  the  last  arch,  which  consists  of  a  single 
hemibranch,  the  respiratory  system  is  practically  the  same  for 
the  first  three  arches;  so  that  the  following  description,  which 
is  taken  from  the  first  arch  of  a  7o-pound  Polyodon  will  answer 
for  all.  The  main  afferent  and  efferent  branchial  arteries 
(Fig.  17,  A.Br.A.  and  E.Br.A.)  maintain  practically  the  same 
positions  and  connections  as  in  other  fishes.  An  afferent  fila- 
ment artery  (Fig.  17,  A.Fil.A.)  is  given  off  distad  from  the 
main  afferent  artery,  to  follow  along  the  inner  margin  of  each 
filament ;  its  course  lies  in  the  connective  tissue,  close  to  the 
filament,  and  its  distribution  within  the  filament  is  a  great  deal 
more  complex,  than  with  other  fishes  that  have  been  studied. 
At  regular  intervals  (Fig.  18)  rather  large,  but  short,  cross 
branches  are  given  off,  which  are  connected  in  an  irregular 
manner ;  thus,  forming  a  sort  of  secondary  chain  of  arteries, 
from  which  the  so-called  afferent  transverse  filament  arteries 
(Fig.  18.  A.F.  Tr.A.)  take  their  origin.  The  latter  vessels  fol- 
low a  nearly  parallel  course  with  one  another,  until  near  the 
filament  septa,  when  each  separates  into  from  three  to  six 
branches,  each  of  which  furnishes  the  venous  supply  for  a 
respiratory  septum.  In  a  7<>pound  Polyodon  the  faces  of  these 
septa  were  about  .1  mm.  apart,  which  as  shown  by  Figs.  18 
arid  i8a  must  contain  about  the  finest  capillary  network  that 
exists.  At  the  outer  margin  of  each  septum  the  respiratory  net- 
work is  collected  by  a  rather  short  efferent  transverse  filament 
artery  (Fig.  18,  E.F.Tr.A.),  which  empties  directly  into  the 
efferent  filament  artery ',  and  all  these  vessels  (Figs.  17  and  18, 
E.Ftl.A.)  pass  proximad  along  the  outer  surface  of  the  fila- 
ments, to  discharge  themselves  in,  and  form,  the  great  efferent 
branchial  arteries  (Fig.  17,  E.Br.A.). 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    IO7 

From  both  the  lateral  and  mesal  side  of  the  efferent  branchial 
artery,  numerous  branches,  designated  as  nutrient  branchial 
arteries  (Figs.  17  and  20,  N.Br.A.}  arise  to  supply  the  mem- 
branes and  connective  tissue,  overlying  and  underlying  the 
efferent  branchial  artery.  Two  such  branches  were  sent  to  the 
base  of  each  filament.  They  were  found  on  either  side  of  the 
efferent  filament  artery,  a  little  profundus  of  the  lymphatic  net- 
work, but  could  not  be  traced  much  beyond  the  base  of  the  fila- 
ment. Many  branches  were  given  off  to  the  gillrakers,  and 
forking  to  follow  the  dorsal  and  ventral  surfaces  of  two  adjacent 
rakers,  they  break  up  into  a  fine  network  in  the  membrane 
connecting  them  (Fig.  17,  G.R.N.}.  Also  very  fine  arterial 
twigs  as  d,  Fig.  20,  were  frequently  seen  in  the  region 
bordering  the  filaments,  but  no  connections,  not  even  with  the 
aid  of  a  microscope,  could  be  established  with  the  so-called 
lymphatic  network. 

What  is  designated  as  the  branchial  arch  artery1  (Fig.  17, 
Br.A.A.}  approaches  the  arch  from  the  anterior  dorsal  corner. 
Shortly  before  the  arch  is  reached  it  bifurcates.  A  large  outer 
fork  (Br.A.A.(i))  is  given  off  to  supply  the  outer  surface  of  the 
arch,  while  the  inner  fork  immediately  makes  a  sharp  curve  to 
pass  to  the  cephalic  margin  of  the  arch,  and  continues  parallel 
with  the  lymphatic  trunk.  It  is,  however,  a  more  profundus 
vessel,  traveling  for  a  good  part  of  its  length  in  a  muscle  over- 
lying the  inner  surface  of  the  arch.  Branches  are  frequently 
given  off  to  the  muscle  and  the  distal  membranes,  and  they  are 
often  accompanied  on  either  side  and  sometimes  nearly  sur- 
rounded by  the  so-called  lymphatics.  The  caliber  of  the 
branchial  arch  artery  and  its  branches  is,  however,  only  minia- 
ture, when  compared  with  the  corresponding  lymphatic  canals. 

At  this  point  there  arises  an  apparent  inconsistency.  In  all 
other  parts  of  the  head  region  in  Polyodon  we  have  arteries, 
veins,  and  lymphatics,  running  parallel  with  one  another,  but  in 
the  branchial  arch  and  filaments  (not  taking  the  respiratory  sys- 
tem into  consideration)  only  arteries  and  lymphatics  have  been 
described.  If  peripheral  connection  had  been  established  be- 

JThe  source  of  this  artery  from  the  dorsal  extremity  of  the  efferent  branchial 
artery  has  not  been  worked  out  as  carefully  as  it  should  have  been. 


108  ALLEN 

between  these  so-called  lymphatics  and  the  nutrient  arteries, 
one  might  claim  that  these  branchial  lymphatics  are  nutrient 
veins,  which  receive  a  network  decidedly  lymphatic  in  charac- 
ter, that  is  continuous  from  the  great  trunk  passing  through  the 
gills  to  the  main  trunk  of  the  branchial  arch,  and  which  may 
function  both  for  a  venous  and  a  lymphatic  system,  terminating 
above  in  a  lymphatic  trunk  and  below  in  a  vein. 

Possibly  it  should  be  noted  here  that  the  fourth  or  last 
branchial  arch  has  but  one  row  of  filaments,  and  is  therefore  a 
hemibranch.  Except  for  some  variation  in  connection  with  the 
efferent  branchial  artery,  which  will  doubtless  be  fully  noted  in 
a  forthcoming  paper,  by  Mr.  E.  P.  Allis  on  the  blood  vessels  of 
Polyodon,  the  lymphatics  and  the  blood-vascular  systems  of  the 
fourth  arch  correspond  very  closely  to  a  hemibranch  of  one  of 
the  other  arches. 

Dorsal  and  Ventral  Endings  of  the  Branchial  Lymphatic 
Trunks  (Nutrient  Branchial  Veins?). — Great  variation  is 
shown  not  only  in  the  dorsal  and  ventral  terminations  of  these 
trunks  in  different  specimens,  but  also  on  the  opposite  sides  of  the 
same  specimen.  In  tracing  out  the  culmination  of  these  vessels 
I  found  it  frequently  useful  to  insert  a  canula  into  one  of  these 
trunks  and  force  water  with  the  aid  of  a  syringe  into  the  trunk ; 
and  having  previously  removed  a  portion  of  the  sinus  or  trunk 
into  which  it  is  discharged,  note  the  orifice  through  which  the 
water  was  ejected. 

Fig.  i  shows  the  dorsal  endings  of  the  branchial  lymphatic 
trunks,  as  seen  from  the  left  side  of  a  7o-pound  Polyodon,  and 
Figs.  2  and  3  represent  the  dorsal  mode  of  termination  of  these 
trunks  on  the  opposite  sides  of  a  25-pound  Polyodon.  In  every 
case  \htfirst  branchial  lymphatic  trunk  (Br.L.  T^i))  bifurcates 
when  about  to  leave  the  arch.  In  Fig.  i  the  ventral  fork 
(Br.L,.  T.(i'))  continues  cephalad  in  about  the  same  plane  until 
the  hyo-opercularis  sinus  is  reached,  when  it  bends  dorsad  to 
follow  along  the  mesal  surface  of  the  hyo-opercularis  sinus  for 
a  short  distance,  and  immediately  after  receiving  the  dorsal 
fork  (Br.L.  T.(i"))9  the  combined  trunk  opens  into  the  hyo- 
opercularis  sinus  through  the  inner  wall  (Br.L.  T.(i)O.).  With 
the  specimen  from  which  Figs.  2  and  3  were  drawn,  both  of 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS 

these  forks  opened  separately  into  the  hyo-opercularis  sinus ; 
the  only  difference  on  the  two  sides  being  that  on  the  right  side 
(Fig.  3)  the  openings  were  further  apart.  In  every  case  the 
ventral  fork  followed  along  the  anterior  margin  of  the  first 
branchial  levator  muscle,  and  the  dorsal  fork  traveled  along  be- 
hind the  same  muscle. 

The  final  dorsal  termination  of  the  second,  third  and  fourth 
branchial  lymphatic  trunks  are  so  different  in  these  three  dis- 
sections that  a  brief  description  should  accompany  each,  al- 
though a  far  better  idea  can  be  obtained  by  carefully  comparing 
Figs,  i,  2  and  3.  In  Fig.  i  the  third  branchial  lymphatic 
trunk  unites  with  the  fourth,  behind  the  posterior  border  of  the 
third  and  fourth  branchial  levator  muscles,  and  the  common 
trunk  (Br.L.  ^.(3)  and  (4))  continues  dorsad  behind  the  muscle 
until  the  jugular  is  reached,  when  it  receives  from  in  front  the 
second  branchial  lymphatic  trunk  (dorsal  fork  of  the  second 
branchial  lymphatic  trunk?),  and  the  combined  trunk  (x)  after 
crossing  over  the  jugular  empties  into  the  cephalic  trunk,  a  short 
distance  behind  the  hyo-opercularis  sinus.  In  Fig.  2  the  fourth 
branchial  lymphatic  trunk  unites  with  a  rather  large  branch  that 
comes  up  from  the  pharyngo-clavicularis  muscle,  and  very 
shortly  is  joined  from  the  rear  by  the  third  branchial  lymphatic 
trunk.  The  course  of  this  common  trunk (Br.L.  ^.(3)  and  (4))  is 
then  obliquely  dorsad,  following  along  the  inner  surface  of  the 
second  branchial  levator  muscle  ;  it  soon  collects  the  dorsal  fork 
of  the  second  branchial  lymphatic  trunk,  and  the  combined  trunk 
thus  formed  (#),  discharges  itself  mesad  of  the  hyo-opercularis 
sinus  in  the  ventral  fork  of  the  cephalic  trunk.  The  remain- 
ing ventral  fork  of  the  second  branchial  lymphatic  trunk 
(Br.-L.T. (2))  travels  mesad  of  the  first  and  second  branchial 
levator  muscles,  and  likewise  terminates  in  the  ventral  fork  of 
the  cephalic  trunk,  a  little  below  trunk  (x).  In  Fig.  3  the  third 
branchial  lymphatic  trunk  makes  a  sharp  curve  on  the  outer 
surface  of  the  arch,  where  it  receives  a  common  trunk,  formed 
from  the  union  of  the  fourth  branchial  trunk  with  a  vessel  com- 
ing from  the  occipito-clavicularis  muscle  and  the  region  behind 
the  fourth  branchial  arch.  The  dorsal  fork  of  the  second 
branchial  lymphatic  trunk  after  traveling  along  the  posterior 


HO  ALLEN 

edge  of  the  second  branchial  levator  muscle,  makes  a  curve  at 
right  angles  to  pass  obliquely  ventrad  along  the  inner  surface  of 
the  second  branchial  levator  muscle,  where  it  shortly  bifurcates 
at  right  angles,  one  fork  continuing  obliquely  ventrad  terminates 
in  the  dorsal  arm  of  the  great  bend  of  the  combined  trunk  from 
the  third  and  fourth  arches,  while  the  other  fork  passes  dorso- 
cephalad  for  a  short  distance  and  receives  a  large  communicat- 
ing branch  from  the  combined  trunk  of  the  third  and  fourth 
arches,  thus  forming  trunk  (#•),  which,  after  bending  at  right 
angles,  passes  dorso-caudad  to  discharge  itself  in  the  cephalic 
trunk,  a  little  behind  the  hyo-opercularis  sinus.  As  on  the 
opposite  side,  the  ventral  fork  of  the  second  branchial  lymphatic 
trunk  empties  into  the  ventral  fork  of  the  cephalic  trunk. 

Only  a  few  of  the  so-called  lymphatics  from  the  branchial 
arches  have  been  traced  out,  and  they  either  terminated  in  the 
main  branchial  trunks  or  in  the  ventral  fork  of  the  cephalic 
trunk.  In  Fig.  3  the  trunk  from  the  first  arch  culminated  in 
the  ventral  fork  of  the  first  branchial  trunk,  at  a  point  indi- 
cated by  £r.A.L.7\(i)9  and  the  one  from  the  third  arch 
(Br.A.L.T.(3))  ended  in  the  ventral  fork  of  the  cephalic 
trunk,  directly  above  the  opening  of  the  ventral  fork  of  the  sec- 
ond branchial  trunk. 

Ventrad,  the  termination  of  the  first  two  branchial  lymphatic 
trunks  in  the  inferior  jugular  are  practically  the  same  for  all 
the  specimens,  but  considerable  variation  exists  in  regard  to 
the  endings  of  the  third  and  fourth  trunks,  both  in  different 
specimens  and  on  the  opposite  sides  of  the  same  specimen. 

As  shown  in  Fig.  5  the  first  and  second  branchial  lymphatic 
trunks  (Itr.Z,.T.(i)  and  (2)),  in  their  ventral  course,  finally 
get  to  lie  immediately  behind  their  corresponding  afferent 
branchial  arteries.  When  close  to  the  ventral  aorta,  the  sec- 
ond trunk  crosses  over  the  ventral  surface  of  the  second 
afferent  artery,  then  passing  cephalad,  in  close  proximity  to 
the  ventral  aorta,  it  crosses  below  the  second  obliquus  ventralis 
muscle  to  anastomose  with  the  first  trunk.  Both  the  first  and  sec- 
ond branchial  trunks  communicate  above  with  the  inferior  jugu- 
lar. The  former  connection  (Figs.  5,  6  and  7,  Hr.L.  T.(i)  V.O.) 
leads  up  between  the  sterno-hyoideus  tendon  and  the  ventral 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    III 

aorta,  and  the  first  afferent  branchial  artery  and  the  second 
obliquus  ventralis  muscle ;  so  far  as  could  be  ascertained  it 
was  the  first  vessel  to  join  the  inferior  jugular.  The  latter 
connection  (Figs.  5,  6  and  7,  J3r.L.T.(2}V.O.)  passes  up 
between  the  second  obliquus  ventralis  muscle,  ventral  aorta, 
and  second  afferent  branchial  artery.  In  the  specimen  from 
which  Figs.  5  and  6  were  drawn  there  was  a  large  dorsal  open- 
ing in  the  inferior  jugular  (Fig.  6,  Af.O.),  which  in  front  lead 
into  a  sinus  designated  as  (M)  that  received  two  sacs  from  the 
rear  (^).  Into  the  left  sac  the  corresponding  fourth  branchial 
lymphatic  trunk  empties,  and  the  right  sac  receives  a  short 
trunk  (Figs.  5  and  6,  S.  T.)  that  encircles  the  inferior  jugular, 
and  communicates  below  with  a  ventral  sinus  (S).  En  route  it 
collects  the  fourth  right  branchial  trunk  (Fig.  5,  Br.L,.T.($) 
from  the  rear ;  while  the  remaining  third  left  branchial  trunk 
(Figs.  5  and  6,  J3r.L.T.($))  empties  directly  into  the  inferior 
jugular,  a  little  in  advance  of  sinus  (S). 

In  the  specimen  from  which  Fig.  7  was  drawn  the  third  and 
fourth  branchial  lymphatic  trunks  had  an  entirely  different 
mode  of  ending  from  that  described  above.  No  dorsal  sinus 
emptied  into  the  inferior  jugular,  but  a  ventral  sinus  (Fig.  7,  S) 
was  present  and  occupied  a  similar  position  as  in  Fig.  5.  Its 
communicating  trunk  (S.  T.)  connected  directly  above  with  the 
inferior  jugular  instead  of  encircling  the  right  side  of  the  in- 
ferior jugular  as  in  Fig.  5.  The  ventral  sinus  in  Fig.  7,  S, 
received  the  third  right  branchial  trunk  in  front,  and  in  addition 
the  fourth  left  branchial  trunk  from  the  rear ;  while  the  fourth 
right  and  the  third  left  branchial  trunks  terminated  directly  in 
the  inferior  jugular. 

The  course  of  the  inferior  jugular  in  the  branchial  region  is 
too  irregular  and  complex  to  permit  of  a  description.  Fig.  6 
gives  a  general  idea  of  its  form  and  its  anterior  communications. 
Here  it  is  simply  a  very  thin  irregular  sinus,  conforming  to  the 
general  arrangement  of  the  branchial  arches  and  the  ventral 
aorta  and  its  branches.  In  the  neighborhood  of  the  union  of 
the  third  and  fourth  pair  of  afferent  branchial  arteries  (Fig.  6, 
A.Br.A.($)  and  (4))  it  not  only  surrounds  them,  but  passes 
dorsad  between  them. 

Proc.  Wash.  Acad.  Sci.,  July,  1907. 


ALLP:N 

Like  Acipenser  and  Scaphirhynchus  the  ventricle  of  the  heart 
of  Polyodon  is  conspicuous  for  the  amount  of  lymphoid  tissue 
surrounding  it.  There  is  always  one  large  lymphatic  gland 
encircling  the  anterior  part  of  the  ventricle ;  another  smaller 
one  is  situated  behind  it  on  the  lower  side  of  the  ventricle,  in- 
closing the  greater  portion  of  the  posterior  end  of  the  ventricle. 
It  is  very  singular  in  Polyodon  that  the  coronary  artery ',  which 
supplies  these  glands  as  well  as  the  heart,  comes  from  the  fourth 
right  efferent  branchial  artery  and  approaches  the  heart  from 
the  rear.  When  the  ventral  side  of  the  sinus  venosus  is  reached 
it  trifurcates.  Two  of  these  branches  pass  cephalad  between  the 
auricle  and  the  ventricle,  supplying  each  ;  while  the  third  follows 
along  the  left  and  ventral  border  of  the  ventricle,  and  gives  off 
branches  that  traverse  between  the  surface  of  the  ventricle  and 
these  glands,  supplying  each.  Corresponding  venous  branches 
arise  from  the  anterior  and  left  ventral  side  of  the  ventricle, 
which  likewise  pass  between  these  glands  and  the  ventricle 
to  terminate  in  two  longitudinal  coronary  veins  that  travel 
caudad  between  the  auricle  and  ventricle.  At  the  posterior 
apex  of  the  heart  these  two  veins  anastomose,  forming  the 
common  coronary  vein,  which  discharges  itself  into  the  sinus 
venosus  from  below.  For  the  most  part  the  blood-vascular 
network  lies  between  these  glands  and  the  ventricle.  In  addi- 
tion to  the  vascular  network  described  above  there  is  a  coarser 
and  more  superficial  network,  decidedly  lymphatic  in  the  char- 
acter of  its  meshes,  which  encompasses  these  glands.  This  is 
undoubtedly  a  lymphatic  network,  but  so  far  as  could  be  deter- 
mined it  was  not  collected  by  any  definite  lymphatic  canal. 
Consequently  it  must,  as  Robin  found  in  Torpedo  (op.  cit.,  pp. 
15  and  16),  reach  the  veins  through  the  oesophagus  plexus. 
One  finds  upon  sectioning  this  lymphoid  tissue  surrounding  the 
heart  that  it  somewhat  resembles  the  thymus.  It  consists  of  a 
connective  tissue  framework  which  is  completely  filled  with 
leucocytes.  In  addition  to  the  numerous  blood  vessels  that 
traverse  it,  many  lymphatic  spaces  or  sinuses  were  found 
which  were  filled  with  leucocytes. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    113 

III.     DISTRIBUTION    OF    THE    SUBCUTANEOUS  VESSELS 
IN    LEPISOSTEUS. 

In  this  genus  the  subcutaneous  vessels  of  the  head,  especially 
the  region  adjoining  the  branchial  arches  and  the  heart,  are  far 
more  sinus-like  than  in  Polyodon  or  the  Selachians,  and  in  this 
respect  they  resemble  the  Teleosts.  The  so-called  cephalic 
sinus  in  Lepisosteus  occupies  a  position  entirely  in  front  of  the 
branchial  arches,  which  is  far  cephalad  of  its  position  in  Polyo- 
don or  as  set  forth  by  Hopkins  for  Amia  (of.  cit.,  pp.  371-2), 
and  corresponds  about  to  its  position  in  Scorp&nichthys  and  other 
bony  fishes.  Other  interesting  points  such  as  a  communication 
of  a  so-called  dorsal  pericardial  sinus  with  the  inferior  jugular 
and  separate  dorsal  and  ventral  branchial  trunks  will  be  de- 
scribed at  length  later  on  in  the  text.  Of  the  three  species  of 
Lepisosteus  that  were  studied  no  more  variation  could  be  found 
than  in  different  individuals  of  the  same  species. 

Longitudinal  Lymphatic  Trunks. — With  Lepisosteus  as  in 
Amia  and  the  bony  fishes  there  are  four  such  canals  in  the 
thoracic  as  well  as  in  the  abdominal  and  caudal  regions.  They 
are  respectively  dorsal,  ventral,  and  lateral  in  position.  A 
transverse  section  as  Fig.  16  shows  that  they  are  enveloped  in  a 
mass  of  connective  tissue,  which  is  imbedded  more  or  less  within 
the  myotomes.  To  the  unaided  eye  they  appear  like  cavities 
in  this  connective  tissue.  The  outer  walls  of  these  vessels  lie 
directly  below  the  skin  and  are  frequently  ruptured  upon  remov- 
ing the  horny  exoskeleton.  Except  for  their  enormous  caliber 
and  their  different  cephalic  termination  they  do  not  differ  ma- 
terially from  the  similar  canals  of  Scorpanichthys.  The  great 
lateral  lymphatic  trunks  (Figs.  8,  9,  n,  12  and  16,  L.L.T.) 
upon  approaching  the  thoracic  region  gradually  leave  the  median 
lateral  line  to  assume  a  more  and  more  dorsal  position.  Accom- 
panying the  ramus  lateralis  vagi  each  trunk  passes  beneath  its 
corresponding  pectoral  arch  to  culminate  in  what  has  been  des- 
ignated as  the  occipital  sinus  (Figs.  8,  9,  n  and  12,  Oc.S.) 
instead  of  emptying  into  the  cephalic  sinus  as  in  Polyodon  or 
Amia.  The  dorsal  lymphatic  canal  (Figs.  8,  u,  12  and  16, 
D.L.  Z1.)  travels  along  the  median  dorsal  surface  of  the  trunk, 
and  likewise  has  a  very  different  ending  from  what  Hopkins 


ALLEN 

found  for  Amia  or  from  Scorpcenichthys.  Instead  of  bifurcating 
behind  the  skull  arid  each  fork  terminating  in  the  cephalic  sinus 
as  one  might  expect,  this  canal  when  not  far  from  the  posterior 
end  of  the  skull  passes  ventrad  along  the  left  side  of  the  con- 
nective tissue  separating  the  two  great  lateral  muscles,  and  when 
the  vertebral  column  is  reached  it  bears  off  obliquely  laterad  to 
cross  below  the  exoccipital  portion  of  the  skull  and  terminates  in 
the  anterior  part  of  the  left  branchial  sinus  (Figs.  8,  n  and  12, 
Br.S.)  from  the  inner  side.  In  every  specimen  of  L.  tristcechus 
and  in  several  of  L.  osseus  the  ventral  lymphatic  trunk  (Figs.  8 
and  13,  V.L.  T.)  forked  at  the  level  of  the  base  of  the  pectoral 
fins,  and  each  of  these  branches,  which  immediately  become 
sinus-like,  continues  parallel  until  the  level  of  the  bulbus  arte- 
riosus  is  reached,  when  they  bear  off  at  right  angles  to  pass  be- 
tween the  clavicle  and  pericardium  and  culminate  in  the  corre- 
sponding pericardial  sinuses  (Figs.  8  and  13,  Per.S.).  In  that 
part  of  their  course  which  lies  between  the  pectorals  and  the 
heart  they  are  separated  only  by  a  sheath  of  tough  connective 
tissue,  in  which  there  are  at  least  two  connecting  orifices.  With 
an  equal  number  of  L.  osseus,  as  shown  in  Figs.  14,  15  and  16, 
the  ventral  trunk  did  not  fork  in  the  region  of  the  pectorals,  but 
continued  cephalad  as  a  single  trunk,  and  when  the  heart  was 
reached  it  joined  the  right  pericardial  sinus. 

As  represented  in  Figs.  14,  15  and  16  the  ventral  lymphatic 
trunk  is  accompanied  by  a  ventral  vein  (V.  V.),  which  passes 
to  the  left  of  the  heart  to  discharge  itself  (Fig.  15)  in  the  left 
precava  a  little  laterad  of  the  orifice  of  the  hepatic  vein.  Two 
ventral  arteries  (Figs.  14  and  16,  V.A.)  also  accompanied  the 
lymphatic  trunk  for  a  short  distance. 

Numerous  intermuscular  lymphatic  vessels  (Figs.  8  and  n, 
Intm.L.  V.)  were  given  off  from  either  side  of  the  dorsal  trunk, 
or  from  above  and  below  in  case  of  the  lateral  trunk.  These 
vessels  traversed  superficially  on  the  septa  between  the  myo- 
tomes.  They  doubtless  connected  the  lateral  with  the  dorsal 
and  ventral  trunks  as  in  Scorphcenichthys  and  other  fishes,  but 
this  fact  was  not  established  for  a  certainty  in  Lepisosteus. 

Pericardial  Sinuses.  —  Each  of  these  sinuses  in  Lepisosteus 
(Figs.  8-14,  Per.S.)  occupies  a  like  position  to  a  similar  sinus 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    1 15 

in  Scorp&nickthys  and  Amia.  In  Lepisosteus  it  follows  along 
the  front  and  inner  surface  of  the  pectoral  arch  parallel  with  the 
precava.  Dorsad  at  about  the  level  of  the  last  branchial  arch  it 
communicates  with  what  is  designated  as  the  occipital  sinus 
(Figs.  8-12,  Oc.S.),  which  continues  ventrad,  mesad  of  the 
pericardial  sinus,  and  shortly  after  receiving  the  pectoral  sinus 
(Figs.  8  and  9,  P.S.),  it  again  joins  the  pericardial  sinus  from 
the  inside  through  a  very  large  orifice  (Figs.  8-10,  Oc.S.O.). 
As  already  stated,  in  the  region  of  the  heart  one  or  both  of  the 
pericardial  sinuses  receive  the  ventral  lymphatic  trunk  or  a  fork 
of  it.  After  which  the  pericardial  sinus  proceeds  along  the  lat- 
eral surface  of  the  ventricle,  just  outside  the  parietal  layer  of 
the  pericardium,  and  when  the  bulbus  arteriosus  is  reached  each 
of  the  pericardial  sinuses  has  a  very  large  opening  (Figs.  8,  9, 
13,  14  and  15,  Per.S.O.),  which  leads  into  a  large  canal  that 
passes  mesad  and  empties  into  the  posterior  end  of  the  so- 
called  dorsal  pericardial  sinus.  This  sinus  (Figs.  13  and  15, 
D.Per.S.),  which  is  located  directly  above  the  bulbus  arteri- 
osus, has  the  form  of  an  ellipse  with  its  longest  axis  corre- 
sponding with  that  of  the  fish.  In  a  lo-pound  L.  osseus  its  di- 
mensions were  15  by  8  mm.  There  is  always  a  communication 
above  with  the  inferior  jugular  vein.  In  the  specimen  from 
which  Fig.  15  was  drawn  there  were  two  such  openings,  both 
of  which  were  located  in  the  posterior  half  of  the  sinus,  and 
were  guarded  by  a  pair  of  semi-lunar  valves  (D.Per.S.  V.) 
opening  into  the  vein.  In  this  specimen  there  was  a  third 
aperture  in  the  anterior  dorsal  wall  of  this  sinus,  but  it  led  only 
into  a  small  blind  pocket.  This  mechanism  in  Lepisosteus  re- 
calls a  sort  of  hypothetical  connection  of  the  ventral  pericardial 
sinus  with  a  branch  of  the  inferior  jugular  in  Scorpcenichtkys 
(op.  cit.,  p.  75).  At  the  points  where  the  connecting  branches 
are  given  off  from  the  pericardial  sinuses  to  the  dorsal  peri- 
cardial sinus  two  anterior  pericardial  canals  are  received  (Figs. 
13,  14  and  15,  Per.S.(i)).  These  doubtless  are  nothing  more 
than  the  anterior  continuations  of  the  pericardial  sinuses,  which 
extend  for  a  short  distance  along  the  ventral  surface  of  the 
parietal  layer  of  the  pericardium. 

Occipital  Sinus  (Figs.  8-12,    Oc.S.). — As  will  be  readily 


Il6  ALLEN 

noted,  the  sinus  so  designated  occupies  a  somewhat  similar  po- 
sition to  the  cephalic  sinus  of  Amia,  Polyodon,  and  Salmo.  It 
likewise  receives  the  lateral  lymphatic  trunk  and  is  connected 
below  with  the  pericardial  sinus,  but  does  not  communicate  di- 
rectly with  the  jugular  or  the  precava ;  hence  the  term  cephalic 
sinus  has  been  reserved  for  a  sinus  located  further  cephalad,  that 
corresponds  in  position  to  a  similar  sinus  in  Scorpcenichthys, 
and  which  terminates  directly  in  the  jugular  vein.  The  occip- 
ital sinus  is  therefore  a  spacious  reservoir,  situated  directly  above 
the  epibranchial  of  the  last  branchial  arch,  in  front  and  a  little 
median  of  the  pectoral  arch,  and  immediately  behind  the  last 
branchial  levator  muscle.  It  also  lies  above  and  behind  what 
is  represented  as  the  branchial  lymphatic  sinus  (Figs.  8,  9,  n 
and  12,  Itr.S.),  from  which  it  is  separated  by  a  very  thin  mem- 
brane. A  little  dorsad  and  mesad  of  the  fourth  epibranchial 
bone  there  is  an  orifice  (Figs.  8,  9,  n  and  12,  J5r.S.O.)  in  the 
ventral  wall  of  the  occipital  sinus,  which  communicates  below 
with  the  branchial  sinus.  Laterad  and  a  little  below  the  level 
of  the  epibranchial  of  the  fourth  arch  it  is  in  connection  with,  or 
possibly  might  better  be  represented  as  receiving,  the  pericardial 
sinus.  At  this  point  the  occipital  sinus  passes  ventrad  along  the 
inner  surface  of  the  pericardial  sinus  for  some  distance,  to  again 
communicate  more  ventrad  with  the  pericardial  sinus  (Figs.  8 
and  10,  Oc.S.O.).  No  special  effort  has  been  made  to  work 
out  in  detail  the  distribution  of  the  lymphatics  in  the  pectoral 
fin,  but  nevertheless  in  all  three  species  of  Lepisosteus  a  large 
pectoral  sinus  (Figs.  8  and  9,  P.S.)  was  found  at  the  base  of 
each  pectoral  fin.  With  L.  osseus  it  collected  numerous 
branches  that  traveled  along  the  dorsal  surfaces  of  the  rays 
and  gathered  a  network  from  the  adjacent  membranes.  Only 
one  branch  per  ray,  however,  was  found  in  L.  osseus;  whereas 
in  Scorpcenichthys  each  ray  possessed  two  vessels,  which  col- 
lected a  network  from  the  adjoining  membrane  connecting  two 
rays.  Upon  reaching  the  anterior  proximal  part  of  the  fin  the 
pectoral  sinus  makes  a  bend  at  right  angles,  and  after  crossing 
diagonally  over  the  outer  surfaces  of  the  superficial  and  pro- 
fundus  pectoral  adductor  muscles  it  again  makes  a  curve  at 
right  angles  to  pass  cephalad  between  the  profundus  pectoral 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    II 7 

adductor  muscle  and  the  great  lateral  trunk  muscle,  to  discharge 
itself  in  the  occipital  sinus. 

Branchial  Lymphatic  Sinuses  (Fig.  8,  n  and  12,  Br.S.).  — 
Each  of  these  reservoirs  is  a  cavity  of  considerable  size,  which 
occupies  most  of  the  space  above  the  superior  pharyngeal  region 
between  the  auditory  capsule  and  the  levator  branchial  muscles, 
and  is  separated  from  the  skull  only  by  the  jugular  vein.  Its 
posterior  depth  is  double  the  anterior.  This  difference  in  depth 
is  not  due  to  a  gradual  tapering  down  of  the  sinus,  but  rather 
to  an  abrupt  rise  in  the  level  of  the  floor  a  little  forward  of  the 
center  of  the  sinus ;  so  that  this  sinus  might  almost  be  said  to 
consist  of  an  anterior  and  a  posterior  portion.  The  anterior 
division  lies  directly  mesad  of  the  first  and  second  branchial  leva- 
tor  muscles  (Figs,  n  and  12,  L.Br.A.(i)  and  (2)).  Cephalad 
it  tapers  down  into  a  sort  of  papilla,  which  curves  around  these 
two  branchial  muscles  to  unite  in  front  with  a  papilla  from  the 
hyo-opercularis  sinus  in  forming  the  so-called  cephalic  sinus 
(Figs.  8,  ii  and  12,  Ceph.S.),  which  empties  into  the  jugular. 
Directly  mesad  of  the  first  branchial  levator  muscle  there  is  an 
orifice  in  the  floor  of  the  anterior  portion  of  the  branchial  sinus 
(Figs,  ii  and  12,  D.Br.L.T.(i)O.)  through  which  a  trunk 
formed  from  the  union  of  the  first  dorsal  branchial  lymphatic  trunk 
(Figs.  8  and  9,  D.Br.L.  ^.(i))  and  a  fork  of  the  second  dorsal 
branchial  lymphatic  trunk  is  discharged.  What  might  be  desig- 
nated as  the  posterior  mesal  corner  of  the  left  anterior  branchial 
sinus  receives  the  dorsal  lymphatic  trunk  (Figs.  8,  ii  and  12, 
D.L.T.).  Leaving  now  the  anterior  part  of  the  branchial 
sinus  we  find  that  the  posterior  portion  of  this  sinus  extends 
caudad  and  ventrad  beneath  the  occipital  sinus,  and  in  the 
neighborhood  of  the  epibranchial  of  the  last  branchial  arch  it 
communicates  above  with  the  occipital  sinus  (Figs.  8,  9,  ii  and 
12,  Br.S.O.).  In  L.  osseus  there  is  an  opening  in  the  anterior 
ventro-lateral  corner  of  the  posterior  part  of  the  branchial  sinus 
(Fig.  12,  D.Br.L.T.(2)O.}  through  which  one  fork  of  the  sec- 
ond dorsal  branchial  lymphatic  trunk  is  discharged.  This  ori- 
fice is  situated  almost  opposite  the  space  between  the  second 
and  third  branchial  levator  muscles.  There  is  still  another 
aperture  about  opposite  the  fourth  branchial  levator  muscle 


3l8  ALLEN 

(Fig.  12,  D.Br.L.  T.(s)O.)  into  which  the  third  dorsal  branchial 
lymphatic  trunk  opens. 

In  position  the  branchial  lymphatic  sinus  corresponds  some- 
what to  the  so-called  hyo-opercularis  sinus  and  the  anterior  part 
of  the  cephalic  trunk  of  Polyodon.  Its  inclination  to  become 
separated  into  two  divisions  recalls  the  two  branchial  sinuses  of 
Scorpanickthys  (op.  ctt.,  Pis.  II  and  III;  Figs.  4  and  5, 
Br.L.S.),  which  were  situated  above  the  epibranchials  of  the 
first  and  second,  and  the  third  and  fourth  arches,  respectively, 
but  were  some  distance  laterad  of  their  position  in  Lepisosteus, 
being  located  outside  the  branchial  levator  muscles,  and  the 
space  between  the  branchial  levator  muscles  and  the  skull  in 
Scorp&nichtkys  was  occupied  by  the  anterior  continuation  of 
the  abdominal  sinus  and  the  cranial  lymphatic  trunk  together 
with  the  jugular  vein.  In  Ophiodon  and  Scorpanichthys  no 
branchial  lymphatic  trunks  were  observed,  but  in  the  former 
nutrient  veins  were  found  emptying  directly  into  the  jugular. 

What  is  designated  as  the  hyo-opercularis  sinus  in  Lepisosteus 
(Fig.  n,  Hyo.O.S.)  is  completely  drawn  on  the  right  side  only. 
It  is  a  reservoir  of  considerable  size  situated  on  the  inner  side 
of  the  operculum,  above  the  gills.  So  closely  does  it  adhere  to 
the  operculum  that  it  is  impossible  to  remove  this  bone  without 
rupturing  its  walls.  This  sinus  is  very  much  depressed  and 
conforms  to  the  general  curvature  of  the  body.  As  in  Scorpce- 
nichthys  it  may  be  said  to  end  dorso-cephalad  in  a  papilla,  which 
in  L.  tristceckus  expands  into  a  distinct  sinus  immediately  laterad 
and  cephalad  of  the  first  branchial  levator  muscle,  to  which  the 
name  cephalic  sinus  has  been  given. 

This  sinus  (Figs.  8,  n  and  12,  Ceph.  S.)  is  joined  from  the 
inside  by  the  branchial  sinus,  and  directly  in  front  of  this 
point  of  union  the  cephalic  sinus  bends  at  right  angles  to  pass 
mesad  and  discharge  itself  in  the  jugular  at  a  point  about  oppo- 
site the  cerebellum.  With  L.  tristoechus  the  cephalic  sinus  has 
much  more  the  appearance  of  a  reservoir  than  in  L.  osseus 
(compare  Fig.  n  with  12).  In  the  latter  it  is  nothing  more 
than  a  canal ;  while  even  in  L.  tristwchus  it  falls  far  short  of 
its  size  in  Scorpcemckthys,  and  is  somewhat  smaller  than  the 
corresponding  sinus  of  Polyodon. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS 

The  positions  of  the  cephalic  sinuses  and  their  points  of  ter- 
mination in  the  jugulars  are  about  the  same  as  in  Scorp&nichthyS) 
but  their  connections  and  positions  in  Amia,  Polyodon  and 
Salmo  are  very  different.  Hence  these  somewhat  dissimilar 
sinuses  may  be  only  analogous.  I  take  the  term  cephalic  sinus 
to  be  nothing  more  than  an  arbitrary  name  given  to  a  dorso- 
cephalic  sinus  that  is  in  connection  with  all  the  subcutaneous 
vessels  and  which  terminates  directly  in  the  jugular  vein,  or 
possibly  the  precava  in  some  species. 

Branchial  Lymphatic  Trunks  (Nutrient  Veins?).1  —  These 
vessels  in  Lepisosteus  have  not  been  worked  out  with  anything 
like  the  detail  that  they  were  in  Polyodon.  Each  arch  pos- 
sessed a  dorsal  and  a  ventral  trunk  that  traversed  between  the 
two  rows  of  filaments,  parallel  with,  but  distad  of,  the  afferent 
branchial  artery,  and  which  so  far  as  could  be  ascertained  had 
no  connection  with  one  another.  No  effort  was  made  to  trace 
out  the  origin  of  these  vessels  from  the  filaments,  and  nothing 
more  was  attempted  than  to  follow  these  canals  to  their  ultimate 
termination.  In  Lepisosteus  the  branchial  arches  are  round  and 
only  miniature  when  compared  with  Polyodon.  They  are  sur- 
rounded by  a  spare  amount  of  spongy  connective  tissue,  con- 
taining only  a  few  corpuscles  in  its  meshes  and  a  small  number 
of  blood  vessels. 

The  first  dorsal  branchial  trunk  (Figs.  8  and  9,  D.Br.- 
T.(iJ)  takes  its  origin  a  little  above  the  center  of  the  arch 
from  between  the  two  rows  of  filaments.  Upon  leaving  the 
most  dorsal  pair  of  filaments  it  travels  along  the  anterior 
margin  of  the  first  branchial  levator  muscle,  receives  a  fork 
(Fig.  8)  from  the  second  branchial  trunk ;  then  curving  to  the 
mesal  side  of  the  muscle,  penetrates  the  floor  of  the  anterior 
part  of  the  branchial  sinus,  through  an  opening  (Figs,  n  and 
12,  Br.L.T.(i)O.)  about  opposite  the  first  branchial  levator 
muscle.  The  second  dorsal  branchial  trunk  (Figs.  8  and  9, 
Br.L.T.(2))  arises  in  like  manner  from  the  dorsal  filaments  of 
the  second  arch,  and  after  leaving  the  arch  it  forks  between  the 

1  As  in  the  case  of  the  branchial  trunks  of  Polyodon  the  method  of  forcing 
water  through  these  trunks  and  noting  the  points  of  its  exit  was  resorted  to  with 
advantage  in  Lepisosteus. 


I2O  ALLEN 

second  and  third  branchial  levator  muscles  ;  the  anterior  branch 
continuing  on  across  the  outer  surface  of  the  second  branchial 
levator  muscle,  unites  with  the  first  branch  mesad  of  the  first 
levator  muscles ;  while  the  posterior  branch  passes  mesad 
between  the  second  and  third  branchial  levator  muscles  to  ter- 
minate in  the  anterior  ventral  corner  of  the  posterior  part  of  the 
branchial  sinus  through  an  orifice  designated  in  Figs,  n  and  12 
as  D.Br.L.T.(2)O.  The  third  branchial  trunk  after  leaving 
its  arch  curves  around  the  fourth  levator  muscle  to  culminate  in 
the  floor  of  the  posterior  division  of  the  branchial  sinus  about 
opposite  the  fourth  branchial  levator  muscle  (Figs,  n  and  12, 
D.Br.L.  T.(3)O.);  whereas  the  trunk  from  the  fourth  arch  dis- 
charges itself  in  an  entirely  different  sinus.  Its  opening  (Figs. 
8,  9,  ii  and  12,  Br.L.T.(^)O.)  is  through  the  inner  wall  of 
that  part  of  the  occipital  sinus  which  lies  mesad  of  the  peri- 
cardial  sinus. 

All  of  the  so-called  ventral  branchial  trunks  doubtless  termi- 
nate in  one  way  or  another  in  the  inferior  jugular  vein.  This  is 
certainly  true  for  the  first  three  pairs,  but  the  final  ending  of 
the  last  pair  I  have  never  been  able  satisfactorily  to  trace  out. 
Each  of  these  ventral  branchial  trunks  has  its  source  from  the 
ventral  filaments,  and  traverses  between  the  two  hemibranchs, 
in  company  with,  but  distad  of,  the  afferent  branchial  artery. 
The  first  pair  of  these  vessels  discharged  themselves  through 
two  orifices  (Figs.  14  and  15,  V.£r.L.T.(i)O.)  situated  in  the 
dorsal  walls  of  the  right  and  left  forks  of  the  inferior  jugular, 
directly  in  front  of  their  corresponding  afferent  branchial  arteries. 
In  the  specimen  from  which  Figs.  14  and  15  were  drawn,  the 
second  right  branchial  trunk  joined  the  right  fork  of  the  inferior 
jugular  exactly  in  front  of  the  second  right  afferent  branchial 
artery  through  an  orifice  designated  as  V.£r.L.T.(2)O.  The 
precise  point  of  union  of  the  third  right  trunk  was  not  located, 
but  upon  injecting  this  vessel  ventrad  with  water  it  was  dis- 
charged through  the  opening  of  the  right  fork  of  the  inferior 
jugular  into  the  inferior  jugular  (Fig.  15,  R.I.J.  V.O.}9  indi- 
cating of  course  that  it  came  from  the  inferior  jugular.  In 
the  dorsal  wall  of  the  left  fork  of  the  inferior  jugular,  imme- 
diately behind  the  second  left  afferent  branchial  artery,  there  is 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    121 

an  orifice  (Fig.  15,  E.},  which  leads  cephalad  into  a  pocket 
through  which  water  is  ejected  upon  injecting  either  the  second 
or  the  third  left  branchial  trunks.  Neither  from  dissection  nor 
from  the  water  injection  method  could  the  termination  of  the 
fourth  pair  of  branchial  trunks  be  located.  Undoubtedly,  how- 
ever, they  are  discharged  into  the  inferior  jugular  vein. 

As  shown  in  Fig.  15  the  inferior  jugular  vein  in  Lepisosteus 
arises  in  the  branchial  region  from  two  branches,  which  unite 
immediately  behind  and  above  the  combined  trunk  formed  by  the 
union  of  the  last  pair  of  afferent  branchial  arteries ;  the  right 
fork,  however,  extends  caudad  for  a  short  distance  as  a  blind 
sac.  Thus  formed,  the  main  stem  of  the  inferior  jugular  (I.J. 
V.)>  passes  caudad  above  and  parallel  with  the  ventral  aorta. 
Dorsad  of  the  bulbus,  as  already  noted,  it  receives  one  or  more 
communications  from  below  from  the  so-called  dorsal  pericardial 
sinus  ;  after  which  it  bears  off  obliquely  to  the  left  to  discharge 
itself  in  the  left  sinus  venosus.  It  seems  in  Lepisosteus  that  this 
sinus  is  divided,  and  the  opening  into  the  auricle  below  is  from 
the  left  side  (Fig.  15,  S.  Ven.O).  Both  sinuses  receive  a  pre- 
cava  or  ductus  of  Cuvier,  but  the  hepatic  and  ventral  veins,  so 
far  as  could  be  ascertained,  terminated  in  the  left  precaya. 

IV.     DEDUCTIONS    AND    SUMMARY. 

From  the  preceding  discussion  it  would  seem  that  the  subcu- 
taneous vessels  of  the  Ganoids  occupy  a  position  fairly  well 
between  the  generalized  Selachians  and  the  more  specialized 
Teleosts  or  Batrachians.  There  is  a  vast  difference  between 
the  character  and  distribution  of  these  vessels  in  the  Chondro- 
ganoidea  (the  cartilaginous  ganoids)  and  in  the  Holostei  (the 
bony  ganoids).  Polyodon  as  a  representative  of  the  former 
group  has  non-sinus  subcutaneous  vessels,  which  in  structure 
are  not  very  dissimilar  to  the  corresponding  veins,  and  in  this 
respect  resemble  the  subcutaneous  vessels  of  the  Selachians, 
which  have  been  described  by  many  authors  as  veins.  While  in 
Lepisosteus,  which  is  one  of  the  bony  Ganoids,  many  of  the  sub- 
cutaneous vessels  are  thin-walled  and  decidedly  sinus-like ;  in 
this  respect  resembling  the  conditions  as  found  in  the  Teleosts 
and  Batrachians. 


122  ALLEN 

With  the  Ganoids,  especially  in  the  branchial  region,  it  is  a 
very  difficult  proposition  to  determine  whether  these  subcutan- 
eous vessels  are  lymphatics  or  veins  or  a  common  system  that 
may  function  for  both.  For  the  present,  until  after  the  embry- 
ology has  been  studied,  and  this  system  has  been  worked  out  in 
the  Cyclostomes,  it  has  seemed  best  to  leave  it  as  an  open  ques- 
tion. These  vessels  have,  however,  in  this  paper  been  described 
as  lymphatics  for  the  following  reasons :  In  every  part  of  the 
head,  excepting  the  branchial  region,  each  of  the  main  subcu- 
taneous canals  is  accompanied  by  a  corresponding  artery  and 
vein,  and  frequently  the  arterial  and  venous  branches  are  sur- 
rounded on  either  side  by  branches  of  these  subcutaneous  ves- 
sels. They  receive  a  superficial  network,  which  is  distinctly 
lymphatic  in  the  character  of  its  meshes,  and  which  is  often 
continuous  with  another  subcutaneous  canal  of  the  same  class, 
and  never  to  my  knowledge  with  a  corresponding  arterial  trunk. 
Excepting  the  branchial  trunks,  as  far  as  could  be  ascertained, 
all  of  the  subcutaneous  canals  contain  a  predominance  of 
white  corpuscles ;  although  in  some  of  the  trunks  they  may  be 
very  scarce.  If  the  longitudinal  subcutaneous  canals  of  the 
trunk  were  considered  as  veins  it  would  be  necessary  to  treat 
them  as  a  separate  venous  system,  that  had  no  counterpart  in 
the  arterial  system.  As  in  the  Teleosts  the  principal  arterial 
trunks  of  this  region  are  the  aorta  and  the  caudal  artery  which 
are  accompanied  by  the  cardinal  and  caudal  veins.  From  these 
vessels  are  given  off  or  received  the  neural,  haemal,  and  the 
lateral  branches,  which  extend  to  the  skin  and  fins  to  supply  or 
collect  the  blood  from  the  region  drained  by  the  superficial 
longitudinal  trunks. 

So  far  as  could  be  determined  in  the  branchial  region  of  the 
Ganoids  there  is  a  nutrient  branchial  arterial  system,  but  no  nu- 
trient venous  system  was  observed  unless  the  so-called  branchial 
lymphatic  system  functions  for  both  veins  and  lymphatics.  In 
JLepisosteus  each  arch  had  a  dorsal  and  ventral  branchial  trunk, 
the  latter  terminating  below  in  the  inferior  jugular  and  the 
former  in  a  branchial  sinus,  which  was  in  connection  with  the 
cephalic  and  pericardial  sinuses.  With  Polyodon  but  one 
branchial  lymphatic  trunk  travels  between  the  branchial  fila- 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    123 

ments  of  an  arch.  Throughout  its  course  it  collects  a  rather 
coarse  network  of  capillaries  from  the  filaments,  which  is  in 
direct  communication  with  what  is  designated  as  the  branchial 
arch  lymphatic  trunk,  and  further  this  network  on  the  arch  is 
in  connection  with  a  very  fine  and  more  superficial  network, 
which  so  far  as  could  be  learned  had  no  connections  with  the 
corresponding  arteries.  These  branchial  arch  trunks  terminate 
dorsad  either  in  the  common  branchial  trunk  or  in  the  ventral 
fork  of  the  cephalic  canal,  while  the  main  branchial  trunks  in 
Polyodon  discharge  themselves  ventrad  in  the  inferior  jugular 
and  dorsad  in  the  cephalic  canal  and  the  hyo-opercularis  sinus. 

A  comparative  study  of  the  cephalic  sinuses  in  this  group  ap- 
parently does  not  throw  much  light  on  the  phylogeny  of  the 
lymphatic  system.  Polyodon^  the  most  primitive  member  of  this 
series,  has  a  cephalic  sinus,  which  in  position  and  connections 
resembles  a  similar  reservoir  in  Amia  and  Salmo,  while  the 
cephalic  sinus  of  Lepisosteus  is  more  closely  allied  to  a  like 
sinus  in  Scorpanichthys  and  other  Teleosts.  This  reservoir  in 
Polyodon  is  situated  just  mesad  of  the  supraclavicle.  It  re- 
ceives the  great  cephalic  canal  from  in  front  which  drains  the 
entire  head  region,  the  lateral  lymphatic  trunk  from  the  rear, 
and  emits  itself  ventrad  into  the  jugular  vein.  With  JLeptsos- 
teus,  especially  L.  osseus,  this  reservoir  is  hardly  deserving  the 
term  sinus.  It  is  far  cephalad  of  its  position  in  Polyodon^  and 
as  in  Scorp&nichthyS)  lies  about  opposite  the  auditory  capsule. 
From  the  rear  it  receives  the  hyo-opercularis  and  branchial 
sinuses.  The  latter  is  in  connection  with  a  series  of  sinuses  that 
surround  the  branchial  cavity  and  gather  the  subcutaneous  ves- 
sels from  the  remainder  of  the  body,  and  about  opposite  the 
cerebellum  the  cephalic  sinus  discharges  itself  mesad  into  the 
jugular  vein. 

With  Lepisosteus  the  first  in  the  chain  of  sinuses  encircling 
the  branchial  cavity  to  connect  anteriorly  with  the  cephalic  sinus 
is  the  branchial  sinus.  It  lies  between  the  branchial  levator 
muscles  and  the  skull,  and  collects  the  first  three  branchial 
trunks,  the  left  branchial  sinus  receiving  the  dorsal  lymphatic 
trunk.  Posteriorly  each  branchial  sinus  is  in  connection  with  a 
spacious  occipital  sinus,  which  collects  the  lateral  trunk  from 


124  ALLEN 

the  rear.  Ventrad  the  occipital  sinus  communicates  with  the 
pericardial  sinus  ;  then  passing  mesadof  the  latter  it  again  joins 
the  pericardial  sinus  from  below,  after  gathering  in  the  pectoral 
sinus.  The  course  of  the  pericardial  sinus  is  along  the  inner 
and  anterior  margin  of  the  clavicle,  and  shortly  after  receiving 
the  ventral  communication  of  the  occipital  sinus  it  is  usually 
joined  by  a  fork  of  the  ventral  lymphatic  trunk.  Occasionally, 
however,  the  ventral  trunk  does  not  divide,  and  in  that  case  it 
empties  directly  into  one  or  the  other  pericardial  sinuses.  Each 
pericardial  sinus  then  continues  cephalad  along  the  side  of  the 
ventricle,  immediately  outside  of  the  parietal  layer  of  the  peri- 
cardium, and  when  the  bulbus  is  reached,  sends  inward  a  large 
communicating  branch  that  terminates  in  the  so-called  dorsal 
pericardial  sinus.  This  sinus,  which  is  situated  directly  above 
the  bulbus  arteriosus,  has  one  or  two  communications  above 
with  the  inferior  jugular,  each  orifice  being  guarded  by  a  pair 
of  semilunar  valves  opening  into  the  vein. 

The  subcutaneous  vessels  surrounding  the  branchial  cavity  in 
Polyodon  take  on  the  form  of  canals  rather  than  sinuses.  Situ- 
ated obliquely  at  the  base  of  the  skull  is  the  hyo-opercularis 
sinus,  which  is  formed  from  the  union  of  the  hyo-opercularis 
and  facial  trunks.  The  latter  in  the  main  follows  the  external 
jugular  and  its  facialis  branch,  which  in  the  region  of  the  ad- 
ductor mandibulae  muscles  communicates  through  a  lymphatic 
network  with  the  so-called  anterior  facial  lymphatic  trunk. 
This  vessel  travels  along  the  surface  of  these  muscles  and  ex- 
tends into  the  snout  region.  The  hyo-opercularis  sinus  also 
receives  the  first  branchial  trunk,  and  opens  mesad  into  a  very 
large  cephalic  canal  that  runs  along  the  branchial  chamber 
directly  above  the  jugular.  The  cephalic  canal  receives  a  great 
trunk  from  below,  formed  by  the  union  of  the  second,  third  and 
fourth  branchial  vessels.  When  the  supraclavicle  is  reached 
the  cephalic  canal  tapers  down  into  a  sort  of  papilla  preparatory 
to  emptying  into  the  cephalic  sinus,  and  at  this  point  it  receives 
from  below  what  is  designated  as  the  pericardial  trunk.  This 
vessel  corresponds  only  in  position  to  the  pericardial  sinuses  of 
Lepisosteus  and  other  fishes,  and  in  no  way  is  it  suggestive  of 
a  sinus.  In  fact  no  pericardial  sinuses  were  found  in  the  region 
of  the  heart. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS    125 

Strange  to  say,  in  Poly o don  a  great  mass  of  lymphoid  tissue 
surrounds  the  heart,  which  is  supplied  by  the  coronary  blood 
vessels,  and  from  which  a  lymphatic  network  arises  that  evidently 
reaches  the  veins  through  the  medium  of  the  oesophagus  plexus. 

Only  in  the  caudal  region  of  Polyodon  were  dorsal  and  ven- 
tral trunks  found.  They  were  present  and  extremely  large  in 
the  thoracic  region  of  Leptsosteus  ;  while  in  Polyodon  all  of  the 
subcutaneous  vessels  of  the  trunk  were  very  minute. 


EXPLANATION    OF    THE    PLATES 

PLATE   I. 

Figs,  i  to  17  were'drawn  to  a  scale  from  injected  specimens  ;  18  to  21  are  from 
microscopic  preparations  of  injected  material;  and  22  to  27  are  from  sections. 
In  general  the  arteries  are  stippled,  the  veins  are  cross-barred,  and  the  so-called 
lymphatic  trunks  are  drawn  in  outline.  A  vessel  drawn  in  dotted  outline  signi- 
fies that  it  passes  within  or  behind  a  bone,  muscle  or  organ.  All  outlines  for 
the  microscopic  drawings  were  made  with  a  camera  lucida  and  the  details  were 
filled  in  afterward. 

FIG.  i.  Represents  a  general  lateral  dissection  of  a  7O-pound  Polyodon 
spathula  head  as  seen  from  the  left  side  and  above.  Most  of  the  paddle  or  spoon, 
all  of  the  opercle  and  branchial  arches,  a  part  of  the  shoulder  girdle,  and  the  left 
wall  of  the  brain  case  were  removed  so  as  to  best  portray  the  vessels.  X  \- 

126 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  I. 


Proc.  Wash.  Acad.  Sci.,  July,  1907. 


PLATE   II. 

TIG.  2.     Sketch  of  the  principal  trunks  of  a  25-pound  Polyodon  as  seen  from 
the  left  side.     X  f  • 

Fig.  3.     Same  view  and  specimen  as  above,  but  seen  from  the  opposite  or  right 

side. 

128 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 

C.L.TO. 


PLATE  II. 


J  V.      Ceph.L.T 


Hyo.O.V 
Hyo.CU.T 


Br.LT.oy 
Br.LT.c.)1 


FIG  2, 


LBrV.  Br.A.LJ. 


,o.  3 


Cejah.LT. 


Br.A.LTw 


Hijo.O.V. 


Br.L.T. 


Br.LT.O)' 


PLATE   III. 

FIG.  4.  Shows  the  course  of  the  hyo-opercularis  lymphatic  trunk  and  its  rela- 
tions with  the  corresponding  superficial  branches  of  the  hyo-opercularis  artery 
and  vein,  as  seen  from  the  right  side  of  a  15-pound  Polyodon.  X  f  • 

FIG.  5.  Ventral  view  of  the  termination  of  the  branchial  lymphatic  trunks 
(Nutrient  branchial  veins?)  in  the  inferior  jugular.  25-pound  Polyodon. 
Natural  size. 

130 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  III. 


Fi 


o. 


Fi  G. 


SlEr.  I- 

Gh.  M. 

BrLlwV 

Br.Llca)l/.0. 
A  Bn 


Maa. 


. 

BP.L.T.W 

Cor.  A. 


PLATE   IV. 

FIG.  6.    Deeper  dissection  of  the  same  specimen  as  above. 
FIG.  7.     Similar  view  and  dissection  as  6  of  a  lo-pound  Polyodon.     Natural 
size. 

132 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  IV. 


Fi  G.  6. 


I.L.V. 


Br.LT.wV.O. 
Br.LT.6.) 


Br.L.T.o) 


Fi-e.    7 


......  Br.LT.wV.O 

8r.LT.wV.O. 
P.  L.T.  at 


I.J.V. 


PLATE  V. 

FIG.  8.  Is  from  a  general  lateral  dissection  of  a  small  Lefisosteus  tristcechus 
as  seen  from  the  left  side.  Most  of  the  opercular  and  shoulder  girdle  regions 
removed.  X  f- 

FIG.  9.  Diagram  of  the  left  pericardial  sinus  and  connections  from  a  10- 
pound  Lefisosteus  osseus.  X  f • 

FIG.  10.  Same  specimen  as  above,  showing  opposite  or  right  pericardial 
sinus.  X  f  • 

'34 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  V. 


Fi&lO. 


Oc.S.O.- 
V.LTO.- 

V.LT: 


PLATE  VI. 

FIG.  u.  Dorsal  view  of  the  same  Lefisosteus  tristceckus  as  Fig.  8.  The  dis- 
section on  the  left  side  is  carried  considerably  deeper  than  the  right.  Shows 
especially  the  termination  of  the  cephalic  lymphatic  trunks  in  the  cephalic  sinus, 
and  the  communication  of  the  latter  -with  the  jugular  vein.  X  !• 

FIG.  12.  Similar  view  to  Fig.  u  of  a  id-pound  Lepisosteus  osseus.  Right  side 
not  figured.  X  f  • 

I36 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PTEC.- 

LL.T. "' 

Intm.LV.---' 


Re.  11. 


PLATE  VI. 


Exos. 


-O.L. 

Crb. 

-CE>h.S. 
LBr.Aft)To(3) 

Hyo.0.5. 
•-Br.Ao) 


PEC.  A. 
..Intm.L.V. 

D.L.T. 
LLJ. 


J.V. 


Car  V. 
LLI 


D.LT 


PLATE  VII. 

FIG.  13.  Ventral  view  of  the  same  Lepisosteus  tristcechus  as  Figs.  8  and  n. 
Shows  the  termination  of  the  ventral  lymphatic  trunk  in  the  pericardial  sinuses 
and  the  union  of  the  latter  in  a  dorsal  pericardial  sinus,  which  lies  directly  above 
the  bulbus  arteriosus  and  communicates  with  the  inferior  jugular  above.  X  f  • 

138 


PROC.  WASH.  ACAD.  SCL,  VOL.  IX. 


PLATE  VII. 


Man. 


F.o.13. 


.-V.  L.T. 


PLATE  VIII. 

FIG.  14.  Represents  a  dissection  of  a  lo-pound  Lepisosteiis  osseus  in  the 
region  of  the  heart  as  seen  from  the  ventral  side.  Ventral  walls  of  the  lym- 
phatic sinuses  and  the  right  inferior  jugular  removed  to  show  the  union  of  the 
ventral  lymphatic  trunk  with  the  right  pericardial  sinus,  the  orifice  of  the  latter 
which  communicates  with  the  dorsal  pericardial  sinus,  and  the  termination  of 
the  two  anterior  branchial  lymphatic  trunks  (nutrient  branchial  veins?)  in  the 
right  fork  of  the  inferior  jugular.  X  $• 

FIG.  15.  Is  a  deeper  dissection  of  the  same  specimen  as  14.  Heart,  ventral 
aorta,  most  of  the  efferent  branchial  vessels,  and  the  ventral  walls  of  the  lym- 
phatic sinuses  and  inferior  jugular  removed  to  show  the  points  of  termination  of 
the  branchial  lymphatic  trunks  (nutrient  branchial  veins?)  in  the  inferior  jugu- 
lar, the  pericardial  sinuses  in  the  dorsal  pericardial  sinus,  its  connections  with 
the  inferior  jugular  above,  and  finally  the  discharging  of  the  inferior  jugular  in 
the  sinus  venosus.  X  f- 

140 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX 
V.  Br.LT.oO, 

R.IJ.V.-- 
V.  Br.  L.T. •<$  O.- 


PLATE VIII 


StET-.V. 

--A.Br.A.o) 
E.Br.A.w 
L.I.J.V. 


VEIL 


FioM.f. 


V  Br.LTwQ 


R.I.J.V.. 

V.  Br.  L.TW0, 

R  I.J.V.O 


D.PEr.S. 
D.PEr.S.V 
D.Per.S.V. 


PEr.S.- 
S.i/EH.O 

s.y0 

PEr.  S. 


-StEr.  V 
— -A.Br.A.d) 
V.  Ao. 


A.BrA« 
A.  Br.  A. (3) 

I.  XV. 


PLATE  IX. 

FIG.  16.  Transverse  section  through  a  rather  small  Lepisosteus  osseus  taken 
33  mm.  behind  the  opercle  as  seen  from  the  rear.  Shows  the  main  longitudinal 
lymphatic  trunks  in  section.  Natural  size. 

FIG.  i6a.  Transverse  through  the  ventral  lymphatic  trunk  region  20  mm. 
caudad  of  Fig.  16  as  seen  from  the  rear.  Natural  size. 

FIG.  i63.  Transverse  section  through  the  ventral  lymphatic  trunk  region  20 
mm.  cephalad  of  16  as  seen  from  the  rear.  Note  the  trunk  is  curving  off  to  the 
right  preparatory  to  emptying  into  the  right  pericardial  sinus.  Natural  size. 

FIG.  17.  Represents  the  inner  or  posterior  surface  of  the  first  branchial  arch 
of  a  yo-pound  Polyodon.  Except  at  the  two  extremities  the  gill  rakers  are  cut  at 
their  bases  so  as  to  best  display  the  branching  of  the  lymphatics  (veins?)  over 
the  surface  of  the  arch.  At  one  place  a  few  of  the  inner  branchial  filaments  are 
removed  to  show  the  position  of  the  branchial  lymphatic  trunk  (nutrient 
branchial  vein  ?)  in  relation  to  the  afferent  and  efferent  branchial  trunks.  Pre- 
ceding this  gap  the  filament  lymphatic  network  (nutrient  venous  network  ?)  is 
indicated  on  the  outer  surface  of  several  of  the  filaments.  X  i* 

I42 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


A.Bl 


FIG.  16. 


OES. 


PLATE  IX. 


D.  L.T. 


UI. 


V.A. 


Hep.V. 


'•     V.  L.T. 


FIG.  I  6 a. 


V.V.  j 
V.  L  T. 


V  A. 

V  V. --- 


-V.A. 
-V.LT. 


FIG.  16k 


PER  C. 


Fa.LT 
A  .FiUJ  A,BrA(1) 


N.  &..A 


E.Br.A.d 


o)       BrA.LN 

G.R.L.N. 


Br.F 


FI.G,  17 


r.  L.T  01 


PLATE  X. 

FIG.  18.  Microscopic  preparation  of  an  injected  branchial  filament  of  a  70- 
pound  Polyodon  as  seen  from  above.  The  respiratory  filament  vessels  are 
stippled  and  the  lymphatic  network  (nutrient  filament  veins?),  which  are  shown 
only  in  part,  are  drawn  in  outline.  X  5°-  Reduced  \. 

FIG.  iSa.    A  portion  of  the  filament  respiratory  network.  X45O-  Reduced  |. 

FIG.  19.  Dorsal  view  of  the  lymphatic  (nutrient  venous?)  network  of  a  70- 
pound  Polyodon.  This  network  is  superficial  to  the  septa  that  contains  the  res- 
piratory network,  and  for  the  most  part  the  transverse  vessels  run  parallel  to  the 
spaces  separating  the  respiratory  septa.  Its  meshes  are  more  irregular  and  very 
much  coarser  (compare  with  Fig.  18).  A  longitudinal  filament  lymphatic 
trunk  (nutrient  filament  vein?)  receives  the  network  from  the  two  opposite  fila- 
ments. X5°-  Reduced  f. 

144 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  X, 


-Fit  .L.T 
•  A.  Fil  A. 

FIG.  18 
A.  F.TT.A. 

Jr.  F.LV. 


E.F.Tr.A. 
E.  FilA.1 


Tr  FL.V- 


FilL.N. 


PLATE   XL 

FIG.  20.  A  portion  of  the  outer  surface  of  a  branchial  arch  of  a  yo-pound 
Polyodon  at  the  base  of  two  filaments.  The  main  efferent  branchial  artery, 
which  lies  directly  below  the  efferent  filament  arteries  is  not  figured.  The 
efferent  filament  and  the  nutrient  arteries  are  stippled ;  while  the  branchial  and 
filament  lymphatics  (nutrient  veins?)  are  drawn  in  outline.  X  5°-  Reduced  \. 

FIG.  21.  Like  Fig.  19,  a  dorsal  view  of  the  same  filament  taken  nearer  the 
basal  end  of  the  filament.  Introduced  to  show  the  character  of  the  so-called 
lymphatic  network  on  the  outer  edge  of  the  filament.  X  5°-  Reduced  \. 

146 


PROD.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  XI. 


Fic,  20. 


N.FLIA. 


--N.  Br.A. 
Br.A.LN. 


Fie.  21. 


E.FIU.  RLUL 


PLATE  XII. 

FIG.  22.  Portion  of  a  longitudinal  section  through  the  so-called  cephalic  lym- 
phatic trunk  of  a  i5-inch  Polyodon.  Note  the  papilla  and  the  relative  propor- 
tion of  white  corpuscles  to  red.  X  45°'  Reduced  f . 

FIG.  23.  Transverse  section  through  the  jugular  vein  of  a  i5-inch  Polyodon. 
Note  papilla  here  also  and  that  the  red  corpuscles  predominate.  Outline  sur- 
rounding some  of  the  corpuscles  denotes  plasma  boundary.  X  45°-  Reduced  \. 

i48 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 

FC.T  W.C 


PLATE  XII. 


N.  M 
i   S.M.F. 


FIG.  22. 


W.C. 


W.C. 


W.C. 


FIG.  23. 


PLATE   XIII. 

FIG.  24.  Transverse  section  through  the  so-called  hyo-opercularis  lymphatic 
trunk  of  a  15-inch  Polyodon.  The  section  is  taken  through  a  papilla  near  its 
surface.  In  this  trunk  the  white  corpuscles,  although  verj  scarce,  greatly  pre- 
dominate over  the  red.  X  45°-  Reduced  f . 

FIG.  25.  Similar  section  to  24  through  the  hyo-opercularis  artery.  X  45°- 
Reduced  f . 

I50 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


PLATE  XIII. 


FIG.  24. 


N.  M. 


V.Vas 


FIG.  25. 


S.M.F. 


Ned 


hit 


PLATE  XIV. 

FIG.  26.  Similar  section  to  24  through  the  hyo-opercularis  vein.  Structure 
is  very  similar  to  the  lymphatic  trunk,  but  the  red  corpuscles  greatly  predom- 
inate. X  45°-  Reduced  ^. 

FIG.  27.  A  diagrammatic  transverse  section  through  three  pairs  of  branchial 
filaments  of  Polyodon. 


PROC.  WASH.  ACAD.  Set.,  VOL.  IX. 


PLATE  XIV. 


FlG.  26. 


FIG.  27. 


E.Fil./L 

---Fil. 
-A. Fil. A. 


o    o Fil.L.T. 

-C.T. 

- Fil. 


PLATE  XV. 

FIG.  28.  Is  a  transverse  section  through  the  branchial  lymphatic  trunk  (nutri- 
ent branchial  vein  ?)  of  a  15-inch  Polyodon.  Note  the  predominance  of  red  cor- 
puscles. In  another  portion  of  the  section  the  wall  is  much  thinner.  X  45°- 
Reduced  ^V 

'54 


PROC.  WASH.  ACAD.  Sci.,  VOL.  IX. 


FIG.  28. 


PLATE  XV, 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS   155 


VI.     LIST    OF    ABBREVIATIONS    USED    IN    THE    FIGURES. 


A  or  P  prefixed  to 
right  or  left  ;  a  series 
a. 
A.BL 


Add.M. 

A.Fil.A. 

A.F.Tr.A. 

A.T. 

Au. 

B.Art. 

Br.A.(i}-( 

Br.A.A. 

Br.A.A.(\}. 

Br.A.L.N. 

Br.A.L.  T. 

Br.F. 


Br.L.T.(z}  and  (4). 

Br.L.T.(if). 

Br.L.T.(i"). 

Br.L.T.(2'). 

Br.L.T.(i}O. 

Br.L.T.(i}V.O. 

Br.S. 

Br.S.O. 

c. 

Car.  V. 

Cen. 

Ceph.L.  T. 

Ccph.  S. 

Ccr. 

CL 

C.L.T.O. 

Cor.  A. 

Cr. 

Crb. 

C.T. 

d. 

D.Ao. 


an  abbreviation  signifies  anterior  or  posterior ;  R  or  Z,, 

is  numbered  from  cephalad  to  caudad. 

In  Fig.  i  point  where  injections  were  made  with  Polyodon. 

Air-bladder. 

Afferent  branchial  arteries  i  to  4. 

Adductor  mandibulae  muscles. 

Afferent  filament  arteries. 

Afferent  filament  transverse  arteries. 

Adipose  tissue  in  brain  cavity. 

Auricle. 

Bulbus  arteriosus. 

Branchial  arches  i  to  4. 

Branchial  arch  artery. 

Branchial  arch  artery  for  outer  surface  of  arch. 

Branchial  arch  lymphatic  (venous?)  network. 

Branchial  arch  lymphatic  trunk  (nutrient  branchial  vein?). 

Branchial  filaments. 

Branchial  lymphatic  trunks  (nutrient  branchial  veins?) 
1-4. 

Combined  trunk  formed  by  the  union  of  the  third  and 
fourth  branchial  lymphatic  vessels. 

Ventral  fork  of  the  first  branchial  lymphatic  trunk. 

Dorsal  fork  of  the  first  branchial  lymphatic  trunk. 

Ventral  fork  of  the  second  branchial  lymphatic  trunk. 

Opening  of  branchial  lymphatic  trunk  (i)  into  the  hyo- 
opercularis  sinus,  Polyodon. 

Opening  of  the  first  ventral  branchial  trunk  in  the  in- 
ferior jugular. 

Branchial  sinus,  Lepisostetis. 

Branchial  sinus  opening  into  the  pericardial  sinus. 

Communications  between  the  2  forks  of  the  ventral  trunk. 

Cardinal  vein. 

Centrum. 

Cephalic  lymphatic  trunk,  Polyodon. 

Cephalic  sinus. 

Cerebrum. 

Clavicle. 

Cephalic  trunk  opening  into  hyo-opercularis  sinus  in 
Polyodon. 

Coronary  artery. 

Cranial  wall. 

Cerebellum. 

Connective  tissue. 

In  Fig.  20  capillary  from  nutrient  branchial  artery. 

Dorsal  aorta. 


156 


ALLEN 


Dorsal    branchial   lymphatic   trunks   (nutrient    branchial 

veins  ?)  I  to  4,  Lepisosteus. 

Dorsal  branchial  trunk  openings  into  the  branchial  and 
occipital  sinuses,  Lepisosteus. 

D.L.  T.  Dorsal  lymphatic  trunk. 

D.Per.S.  Dorsal  pericardial  sinus,  Lepisosteus. 

D.Per.S.V.  Semilunar  valves  of  the  dorsal  pericardial  sinus  of  Lepi- 
sosteus opening  into  the  inferior  jugular. 

E.Br.A.(\)-{^}.  Efferent  branchial  arteries  I  to  4. 

E.Fil.A.  Efferent  filament  arteries. 

E.F.  Tr.A.  Efferent  filament  transverse  arteries. 

Enc.A.  Encephalic  artery. 

Enc.  V.  Encephalic  vein. 

End.  Endothelium. 

Ex.  Tunica  externa  (adventitia). 

Exos.  Exoskeleton. 

F.A.  Facialis  artery. 

Fac.M.  V.  Facialis-mandibularis  vein. 

F.C.T.  Fibrous  connective  tissue. 

Fil.  Filament. 

Fil.L.N.  Filament  lymphatic  (nutrient  venous?)  network. 

Fil.L.T.  Filament  lymphatic  trunk  (nutrient  filament  vein?). 

F.L.T.  Facial  lymphatic  trunk. 

F.L. T.(i).  Anterior  facial  lymphatic  trunk. 

F.L.T. O.  Facial  lymphatic  trunk  opening  into  the  hyo-opercularis 
sinus. 

F.  V.  Facialis  vein. 

Gh.M.  Glossohaly  muscle. 

G.R.  Gill  rakers. 

G.R.L.N.  Gill  raker  lymphatic  (venous?)  network. 

G.R.N.  Gill  raker  arterial  network. 

Hep.V.  Hepatic  vein. 

Hyo.A.  Hyoidean  artery. 

Hyom.  Hyomandibular. 

Hyo.O.A.  Hyo-opercularis  artery. 

Hyo.O.A.(i).  Superficial  branch  of  the  hyo-opercularis  artery. 

Hyo.O.L.T.  Hyo-opercularis  lymphatic  trunk. 

Hyo.O.L.T.(i).  Dorsal  branch  of  the  hyo-opercularis  lymphatic  trunk. 

Hyo.O.S.  Hyo-opercularis  sinus,  Lepisosteus. 

Hyo.  O.  V.  Hyo-opercularis  vein. 

Hyo.  O.  V. ( i ) .  Superficial  branch  of  the  hyo-opercularis  vein. 

LJ.V.  *         Inferior  jugular  vein. 

Int.  Tunica  intima. 

Intm.L.V.  Intermuscular  or  transverse  lymphatic  vessels. 

I.  Per.  Visceral  or  inner  layer  of  the  pericardium. 

J.  V.  Jugular  vein. 

Kid.  Kidney. 

L.  Liver. 

L.Br.(i)-(q).  Branchial  levator  muscles  I  to  4. 

L.Br.V.  Branchial  levator  muscle  veins. 


DISTRIBUTION    OF    SUBCUTANEOUS    VESSELS    IN    GANOIDS   157 


L..I.J.  V. 
L.L.T. 


L.N.(2). 


L.  V.L.  T. 

M. 

Man. 

Med. 

M.O. 

My. 
Myo. 

N. 

N.Br.A. 
N.Fil.A. 

N.M. 
N.S. 
o. 

Oc.S. 

Oc.S.O. 

CEs. 

O.L. 

O.Per.S. 

Op.M. 

O.  V.M.(i) 

P. 

Pec.  A. 

Per.  C. 

Per.L.  T. 

Per.S. 

Per.S.(i). 

Per.S.O. 

P.P. 

P.P.Add. 

Prec. 

Prem. 

P.  S. 

P.S.O. 

Pt. 

R.  C. 

Res.N. 

R.Hyom. 

R.I.J.  V. 

R.I.J.V.O. 


Left  fork  of  the  inferior  jugular  vein. 

Lateral  lymphatic  trunk. 

Lymphatic  network  on  surface  of  the  thjmus  gland  and 

adjacent  region,  Polyodon. 
Lymphatic  network  overlying  the  facialis  blood  vessels, 

Polyodon. 

Lymphatic  network  in  hyo-opercularis  region  of  Polyodon. 
Left  fork  of  the  ventral  lymphatic  trunk. 
Dorsal  sinus  emptying  into  the  inferior  jugular,  Polyodon. 
Mandible. 
Tunica  media. 
Orifice  of  the  dorsal  sinus  opening  into  the  inferior  jugu- 

lar, Polyodon. 
Myelon. 
Myotomes. 
Posterior  sacs  of  Polyodon  that  terminate  in  the  inferior 

jugular. 

Nutrient  branchial  arteries. 
Nutrient  filament  arteries. 
Nucleus  smooth  muscle. 
Nasal  sac. 
In  Fig.   15  orifice  of   pericardial  sinus    leading  into  the 

dorsal  pericardial  sinus. 
Occipital  sinus,  Lepisosteus. 

Occipital  sinus  opening  into  the  pericardial  sinus. 
CEsophagus. 
Optic  lobes. 

Parietal  or  outer  layer  of  the  pericardium. 
M.  Opercularis. 

Obliqui  ventrales  muscles  i  to  4. 
Papilla. 
Pectoral  arch. 
Pericardial  cavity. 

Pericardial  lymphatic  trunk,  Polyodon. 
Pericardial  sinus,  Lepisosteus. 
Anterior  continuation  of  the  pericardial  sinus. 
Communications    of    the    pericardial    sinuses   with    the 

dorsal  pericardial  sinus. 
Pectoral  fin. 

Pectoral  profundus  adductor  muscle. 
Precava. 
Premaxilla. 
Pectoral  sinus. 

Pectoral  sinus  emptying  into  the  occipital  sinus. 
Post-temporal. 
Red  corpuscle. 
Respiratory  network. 
Retractor  hyo-mandibularis  muscle. 
Right  fork  of  -the  inferior  jugular  vein. 
Right  fork  of  the  inferior  jugular  opening  into  the  in- 

ferior jugular. 


ALLEN 


R.Lat.X. 
S. 

S.Cl. 

S.M.F. 

S.P.Abd. 

Sptr. 

S.T. 

Ster.  T. 

Ster.  V. 

Sub.  A. 

S.  Yen. 

S.Ven.O. 

Tr.F.L.  V. 

V. 

V.A. 

V.Ao. 


Yen. 

V.L.T. 

V.L.T.O. 

V.V. 
V.  Vas. 
W.C. 
x. 


I. 
II. 

K(2). 

Vand  VII. 

VIII. 

IX. 

X. 


Ramus  lateralis  vagi. 

A  sinus  in  Polyodon,  which  lies  above  the  ventral  aorta 

and  opens  into  the  inferior  jugular  above. 
Supra-clavicle. 
Smooth  muscle  fiber. 
Superficial  pectoral  abductor  muscle. 
Spiracle. 

Communicating  trunk  from  sinus  *S  to  inferior  jugular. 
Sterno-hyoideus  tendon. 
Sterno-hyoideus  vein. 
Subclavian  artery. 
Sinus  venosus. 

Orifice  of  sinus  venosus  leading  into  the  auricle. 
Transverse  filament  lymphatic  vessels  (nutrient  veins?). 
Point  where  cephalic  sinus  joins  jugular  vein. 
Ventral  artery. 
Ventral  aorta. 
Ventral  branchial  lymphatic  trunks  (nutrient  veins?)  I  to 

4,  Lepisosteus. 

Ventral  branchial  trunks  opening  into  the  inferior  jugular. 
Ventricle. 

Ventral  lymphatic  trunk. 
Ventral    lymphatic   trunk   opening    into   the   pericardial 

sinus. 

Ventral  vein. 
Vasa  vasorum. 

White  corpuscle  or  leucocyte. 
Combined  trunk  formed  by  the  union  of  the  third  and 

fourth  dorsal  branchial  trunks  with  the  dorsal  fork  of 

the  second  branchial  trunk. 
Point  of   union  of   the  third   branchia     trunk   with   the 

fourth. 

Olfactory  nerve. 
Optic  nerve. 

Truncus  buccalis  maxillo-mandibularis. 
Trigemino-facial  complex. 
Auditory  nerve. 
Glossopharyngeal  nerve. 
Vagus  nerve. 


FOURTEEN  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 


This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 


MAY  18 


